Bill unlatched the back door of the bank, pushed it open and stood aside for Dorothy to pass through.

"Wait a minute." She put out a restraining hand. The full glare of the arc light in the alley fell on the damp ground at their feet. "Right over there are the tire marks of the holdup car. It's lucky it rained this afternoon. The prints are perfect in this mud."

"Well, that's interesting, but--"

"Oh, no. Of course they won't solve the mystery. That's what you were going to say, isn't it?" Dorothy's voice was mocking as she looked up at Bill. "But here--see these footprints? From this door to the car?" Her tone was triumphant now. "They ought to help just a little, don't you think?"

But Bill seemed unmoved at her discovery. "Probably hoofmarks of the cops," he said rather disparagingly.

Dorothy laughed. "If those footprints were made by policemen I'll eat them. Where are your eyes, Bill? The cops in this town wear regulation broad-toed shoes. When I heard the traffic cop tell Dad that he'd seen the robbers' car go up the alley, I dashed out here to have a look around. And as soon as I saw these prints I knew they were not made by broad-toed boots. Let's examine them closer."

Taking care to avoid stepping on the well defined trail that led from the door to the tire marks of the car, the two studied the line of footprints.

"One fellow wore rubber soled shoes--I guess you're right, Dorothy," acknowledged Bill, squatting on his heels. "The pattern on this set of prints could have been made by nothing else. But what do you make of these tracks here? Just holes in the mud with a flat dab right ahead?"

"High heeled shoes, Bill. One of this gang is a woman, that is clear enough. What bothers me is the third set--look!"

Bill stared at the footprints to which she pointed. "The right-hand one was made by a long, narrow shoe, but I'll swear that boot last was never made in America. It's too pointed," he said finally. "The shoe that made that imprint was bought in southern Europe, I'll bet--Italy, probably. But those queer looking marks to the left are beyond me," he frowned. Then he cried--"No, they're not! I have it--the man who made those prints was club-footed!"

Dorothy disagreed with him. "A club-foot couldn't make that mark. It is too symmetrical--straight on both sides and kind of rounded at the back and front. It wasn't made by a wooden leg, either, Bill!"

"No. That would simply dig a hole in the mud."

"Oh, I know! Why didn't I see it at once!" she exclaimed excitedly--"The man was lame!"

Bill snorted. "And he had long pink whiskers which he tied round his waist with a green ribbon!"

"Don't be silly--I know what I'm talking about."

"How so?"

"I know that a lame man made that set of marks."

"Very well. May Doctor Watson inquire on what Miss Sherlock Holmes bases her astounding deduction?"

"On those queer marks, of course, stupid!"

"Thanks. The clouds have vanished. You make everything so lucid." Bill stood erect once more.

"But, Bill--did you ever see a lame man--whose left leg was shorter than his right?"

"Maybe I did. But I can't swear at this distant date which leg was the shorter."

"Well, I can tell you that in this case, the left was!"

"Maybe--"

"Maybe nothing! Why am I sure of it? Because the man wore a lame man's boot--the kind with a very thick sole. My grandfather wore one. He twisted his hip when he was a boy and that leg didn't grow as long as the other. What is more, he always walked on the sole of his big boot--the heel never touched the ground!"

"I believe you are right," mused the young man, studying one of the queer footprints again.

"I know I am, Bill. That kind of a shoe would make exactly that print. Not such a bad hunch to take a look out here, was it?"

"You're a swell sleuth, Dorothy. Let's see. Now we know there were three in the gang this evening. The chap who played chauffeur and wore sneakers, a woman, and a lame man--probably an Italian."

"Yes. But that doesn't solve the mystery, does it?"

"No, but it helps a lot. How about the tire tracks?"

"Not our car. Daddy uses Silvertowns and those were made by some other kind."

"Goodyears, I should say. How about going in now and telling your father what we've learned?"

"I'd rather not, if you don't mind?"

"Why!"

"Well, you see, Bill, Dad hasn't much confidence in girls' views on what he calls 'the practical side of life'--mine especially. There'll soon be a bunch of detectives on this case. If they find out for themselves, it's O.K. with me--but I shan't tell them."

"You want to work up the case yourself?"

"That's exactly it. If you'll help me?"

"Certainly I will. But we may get into trouble--I mean it is likely to be dangerous work."

"Does that bother you?"

"I'd hate to have you get hurt--"

"I won't do anything on my own without telling you first. We'll work together. Does that suit your highness?"

"You bet! Where do we go from here?"

"Back to my house. We'll go down the alley and hop in your car. I want to ride up to our garage. I've got another hunch."

"The kid's clever," remarked Bill admiringly. "Want to tell me? I haven't a glimmer."

They turned out of the alley into Main Street before Dorothy answered.

"Suppose you guess," she suggested teasingly as she stepped into the car. "Or, better still, now that you've become my aviation instructor, I'll even things up and give you a short course in sleuthing."

"That's a go, teacher," grinned Bill. The car rolled up the hill past the white Memorial Cross on the village green. "But to a mere amateur in crime it looks as though you had barged into a pretty good mystery, no kidding."

"Sh--" commanded Dorothy. "Sherlock Holmes is thinking."

"Don't strain anything," Bill advised as he stepped on the accelerator.

Dorothy did not retort to this thrust, but remainder wrapped in her thoughts for the remainder of the ride. Bill turned the car into the Dixon's drive before she spoke again.

"Keep on to the garage, please."

"Right-oh! Still sleuthing, I take it?"

"Yes."

"What is the big idea?"

"Wait and see."

He drew up under the arching elms with the glare of their headlights focussed upon the closed garage doors. Dorothy sprang out and ran forward.

"Locked," she affirmed, giving the handle a tug. "Wait a minute, Bill. I'll be right back." She disappeared in the direction of the house.

Bill shut off the engine and clambered down to the ground. Presently he saw her coming back, accompanied by a woman in maid's cap and apron.

"All right, Lizzie," her young mistress said, "I want to look at something first. Then you can tell us exactly what happened. That's right, give me the key."

She swung open one of the wide doors.

"The Packard's there, just as I told you, Miss Dorothy," volunteered Lizzie as the three stepped inside the garage. "It's your car that's missing."

"I left it at the beach club--" Dorothy cut herself short. "The license plates are gone from the Packard!"

"Wasn't that to be expected after what the cop told us in the bank?" There was a hint of mockery in Bill's voice.

"Of course. But the point is--were they taken this afternoon while Daddy had the car parked behind the bank--or later this evening after he drove home? He would never remember whether he drove from the bank with the plates still attached or not. He never notices details like that."

Bill seemed amused. "Perhaps not--but what's the difference?"

"Wait a minute. You'll soon get another slant. Now, Lizzie--start from the very beginning."

Lizzie spoke up eagerly. "Yes, miss. Cook and me was havin' our supper in the kitchen, miss--"

"Where was Arthur?--He's our chauffeur-gardener," explained Dorothy to Bill.

"It's Arthur's night off, miss. He went to the movies--said he'd get a bite at the lunch wagon in the village, though why a man should want to eat hot dogs and such trash with honest-to-goodness vittles waiting for him at home is more than--"

"Never mind that now, Lizzie.--You and cook were eating supper--?"

"Yes, miss. We was just finishin' when we heard a car pass the house on its way out to the garage. I thought it might be Arthur, back in the Ford for some supper. Cook said--"

"Oh, Lizzie, please! What happened then?"

"Why, a man came to the back door and asked for the key to the garage. Said as how he had orders to fix the Packard."

"What time was that?"

"About five minutes after we heard the car drive out here, miss."

"No--I mean the time of day."

"I couldn't rightly say, Miss Dorothy. The kitchen clock is down to Whipple's being mended. But it was just after you'd gone over to Mr. Bolton's for dinner."

"What did the man look like, Lizzie?"

"Like any young man, miss."

"But was he tall or short?"

"Kind of medium-like--"

"Dark hair or light?"

"I can't seem to remember--he had a chauffeur's cap on and was in his shirt sleeves, that I do know."

"Did you notice if he limped?"

"No, he didn't, miss--but the other fellow did--him with the big boot."

"Bull's eye!" cried Bill. "You're sure some detective, Dorothy!"

"Keep still?" ordered that young lady. And then to the housemaid: "We'll take up the man with the big boot in a minute, Lizzie. Now then, you gave the other one the garage key, I s'pose?"

Lizzie snorted. "That I didn't, miss. I took the key off the hook and walked out to the garage with him. Mr. Dixon wouldn't be thankin' me to let strange men fool round in the garage by theirselves!"

"Then how in thunder did they cop the license plates without your seeing them?" exploded Bill.

"Do shut up and let me talk!" Dorothy stamped her foot impatiently. "Now, Lizzie, what happened next?"

"Well, miss, I unlocked the doors and he started tinkerin' with the engine of the Packard there. Then all of a sudden he went out to the other car and spoke to somebody inside."

"What car was that?"

"The one he'd drove up in. It was parked out on the drive where the young gentleman has his'n now."

"Another Packard, was it?"

"I couldn't say, miss. I didn't pay much attention to it, except that it was a closed car--and there was a man and a woman in back."

Dorothy exchanged glances with Bill. "And then?"

"Then the young feller comes back and says as how the lady in the car was feeling sick, and could I fetch her a glass of water with a teaspoonful of bicarbonate of soda in it. I knew we had some in the medicine chest upstairs, so--"

"So you went back to the house and got it?"

"Yes, miss."

"And that's when they copped the plates!" declared Bill, the irrepressible.

"Bull's eye!" derided Dorothy. "How'd you guess it?"

"Form of genius some of us have."

Dorothy ignored this last and turned again to the maid. "What happened when you brought back the bicarb, Lizzie?"

"I give it to the young lady in the car, miss."

"Young, was she?"

"I couldn't get a good look at her face, for she was dabbin' her eyes with a handkerchief like she'd been cryin'. But she was dressed in some of those new-fangled pajamas like you wear to the beach, they was--sort of yellow-green color--and a wisp of her hair that had got loose from the bandanna she wore was red--the brightest red hair I ever see. She turned her head away when she drunk the medicine, but she thanked me prettily enough when she handed back the glass."

"Have you washed it yet?"

"No, miss. You see, I--"

"Then don't. I want that glass, just as it is. Was the lame man sitting beside her?"

"No. When I brought her the soda he was comin' out of the garage with the other fellow. He was carryin' a package wrapped in newspaper and he says as how he was takin' some part of the engine back to the shop. He spoke kind of funny, like a foreigner, I thought. And all dolled up in a light suit and a cane. Why, he'd even got lemon colored gloves on for all his lameness and the big boot he wore!"

"Did the girl and the other man wear gloves?"

"The man put them on when he started to tinker with the car, I remember. But the girl had no gloves on."

"You're sure?"

"Oh, yes, miss, because I noticed her shiny pink finger nails, particular. I thought at the time that washin' dishes couldn't be no part of her life."

"That's fine, Lizzie. You make a splendid witness."

"Thanks, miss. I got a good look at the lame man, too. He had a funny little black mustache like they wear in the movies and little gold knobs in his ears--what do think of that!" Lizzie paused dramatically as she gave this choice bit of information.

"Earrings?"

"Earrings, miss--and--"

"Thank you, Lizzie. You may go now."

"Remember those earrings, miss. And I'll keep the glass for you, and won't let cook touch it either, never fear!" Lizzie's slight figure faded into the darkness.

"So you've got pretty good descriptions of the gang and the lady's fingerprints!" Bill summed up. "I've got to hand it to you, kid. Reckon you'll have to let your father know about it though. Those fingerprints will have to be examined by the police."

Dorothy nodded. "Guess you're right. I'll tell him what we found out."

"What you've found out, you mean. As I think I told you before, when it comes to detective work, I'm a ground hog!"

"Nonsense! But that reminds me, Bill. Do I get a lesson tomorrow?"

"Do you think you can take time enough from your life work?"

"Don't be ridiculous. You may think I've finished fooling with this robbery when I turn over the dope to Daddy--but I haven't. I want a flying lesson, just the same, in the morning. Shall we go up in the Loening again?"

"No. I'll drive you down to the shore and we'll take the N-9 out. Don't wait for your father to-night. Tell him what you want to at breakfast."

"But I've got to--"

"This is your flight instructor speaking, Dorothy. No lesson in the morning for you, young lady, unless you go straight to bed now and get a good night's rest. A clear head and steady nerves are the first requisites for flying."

"All right then. I'll turn in directly. Good night."

Bill was already seated behind the wheel of his car. "Good night, Dorothy. By the way, I've got a hunch about this bank business. After you've had some flight training we'll investigate together--and the plane will be a great asset," he added mysteriously. His foot pressed the self-starter.

"Don't be so vague--spill the news like a good fellow."

"Sh--" mocked Bill. "'Sherlock Holmes is thinking!'" His laugh rang out and the car disappeared in the deep shadows of the drive.

"He's not so dumb as he pretends," mused Miss Dixon. "What can he have up his sleeve?"

Slowly she moved off toward the back door of the house.