The December evening was cold and wet as Dorothy and Ashton Sanborn crossed the sidewalk and entered their taxi-cab. The day had been a dreary one, and now a dense, drizzling fog lay low upon the great city. Dun-colored clouds drooped over a muddy Park Avenue as they were swept up town. On the side streets the electrics were but misty splotches of diffused light which threw feeble circular glimmers upon the slimy pavements. The yellow glare from shopwindows streamed out into the chill, vaporous air, and threw a murky, shifting radiance across the crowded thoroughfare. To Dorothy there was something eerie and ghostlike in the endless procession of faces which flitted across these narrow bars of light. She was not in any respect a timid girl, but the dull, heavy evening, and the prospect of the strange venture in which they were engaged, combined to make her feel nervous and depressed.

At 59th street the taxi turned west and rolled steadily along the shining black asphalt, stopping now and then for the red lights. They crossed 5th Avenue and swung into Central Park. Dorothy caught glimpses of the gaunt shapes of trees in silhouette against the cold fog. She closed her eyes and resolutely turned her thoughts to the events of the afternoon.

So engrossed had she become in the contemplation of her delightful buying orgy that she was surprised when their cab pulled up with a jerk and Ashton Sanborn opened the door.

“Muffle up in your fur collar, Dorothy,” he said. “The fewer people who see your face, the better.”

Now that the ordeal had arrived, Dorothy’s nervousness vanished. She buried the lower part of her face in the soft fur collar and walked at Mr. Sanborn’s side into the lobby of the apartment house.

A darkey in brass buttoned uniform stood by the elevator. Two shining rows of white teeth flashed in a smile of greeting for the detective.

“All the way up, George.” Mr. Sanborn gave the order as the car started upward.

“Yaas, suh, boss, I understand.” George smiled again, and presently the elevator stopped.

With Mr. Sanborn in the lead, Dorothy walked along a corridor and up a narrow flight of stairs. The detective opened a door at the top and the damp cold of the night swept in upon them. A moment later they were crossing the flat roof of the apartment house toward a small group who stood near the parapet at the roof’s edge. As they drew nearer, she saw that the group awaiting them was composed of Bill Bolton, Howard, and a stranger. They were standing beside a small crane.

The secret service man nodded a greeting and turned to Dorothy. “We are directly above Janet’s window, which is three flights below,” he said quietly, and glanced at the luminous dial of his wrist-watch.

“And you’re going to let me down with the auto-crane?” she asked with just a tremor of excitement in her voice.

“That’s the idea. It’s perfectly safe. Bill tested it this afternoon.”

Dorothy gave a little laugh. “Oh, I’m not scared, Uncle Sanborn.”

“I know you aren’t, my dear.”

“When do I take off?”

“Whenever you’re ready.”

“All set now, then, please.”

“Good. You’ll go in a minute. Here are last instructions. You will seat yourself in that swinging seat that Bill is holding. The cable to which it is attached runs through the pulley at the end of the crane’s arm. This building is nine stories high. The Jordans’ flat is on the seventh floor, you remember, so Janet’s window is the third one down.” He moved to the low parapet and leaned over. “The window is dark, so everything is O.K.,” he said, coming back to her. “Pull your seat in with you when you enter, Dorothy, and pull down the shade, of course, when the light is turned on. When Janet is ready, switch off the light again and have her give a couple of pulls on this guide rope.” He placed the rope in her hand. “Then we will hoist her up. Ready for your hop now?”

“Yes, thanks.”

“Good luck, then. And remember that although you may not see us, I or some of my men will be near you all the time.”

Dorothy shook hands with her three friends and stepped into her swinging seat. She sat down, steadying herself with a grip on the cable.

“All serene?” asked Bill.

“Shove off!” said Dorothy.

Bill motioned to the stranger, there came the low whir of an electric motor. Her feet left the roof and she felt herself swung upward. Then the ascent stopped, the arm of the crane swung outward and with it her pendant seat. Her feet cleared the parapet and she was over the narrow airshaft.

Blurred lights from closed windows of the various apartments gave her a glimpse of many empty ashcans in the small courtyard far below. But the crane was lowering her now close to the wall of the building. She was facing the wall, and looking upward she made out four heads leaning over the parapet at the edge of the roof.

The descent was slow, but at last she passed two windows and came to rest beside the third, whose lower sash she saw was open. Then two arms caught her about the knees and she was pulled into the room.

“Dorothy—oh, Dorothy!” sobbed an excited voice so like her own that Dorothy gave a start.

“Well, here I am, Janet.” It was a prosaic reply, but her own heart was beating quickly, nevertheless. “Gee, it’s dark in here! Be a dear and shut down the window on this cable—and draw the shade, then turn on the light. I’m busy getting out of this thing.”

She heard the window and shade come down with a rush. As she stepped free of her conveyance, the lights flashed on, and the cousins flew into each other’s arms.

“Janet!”

“Dorothy!”

For a long moment the girls hugged each other and Janet, the more over-wrought, sobbed on her cousin’s shoulder.

Dorothy was herself deeply touched, but managed to control her feelings. “Come, dear,” she said at last. “We’ll just have to get going, I guess. They’re waiting for you on the roof—and somebody is likely to come to the door. We mustn’t be caught together, you know.”

“I know it.” Janet released her and again Dorothy gasped, for she heard her own voice speaking although the words came from Janet.

“Look, Dorothy!” Janet pointed to a long mirror in the corner of the room. “I knew that we were a lot alike, but I never could have believed—”

“Well, talk about two peas in a pod!” In the glass Dorothy saw herself standing beside her cousin; and had it not been that she wore a coat and hat, while Janet was dressed in a wine-colored silk frock, she would have had difficulty in knowing which was her own reflection. “Maybe I’m half an inch taller, or hardly that,” she said after a bit. “Lucky we both have had our hair shingled. You wear a bang, though—but that’s easily fixed.”

She whipped off her small hat and went over to the dressing table where she picked up a pair of nail scissors. Two minutes of snipping and Janet’s bang was duplicated on her own forehead. The hair she had cut off had been carefully placed on a magazine cover and opening the window a trifle she dropped the ends into the night.

“Now,” she said, closing the window. “You and I had better change clothes, Janet. And we’ll have to make it snappy.”

“Yes—and oh dear—” Janet was slipping off her dress—“I’ve got so much to talk about. You can’t realize what a horrible time I’ve had—and then to find you, only to lose you again!” Janet was very near to tears.

“But you won’t lose me long,” Dorothy flashed her a comforting smile as she got out of her own dress. “Meanwhile, you’ll have Howard. He’s waiting on the roof, now. And Ashton Sanborn says he can clear up this business in a few days.”

“You certainly are wonderfully brave to do this for me,” sighed her cousin. “If Mr. Sanborn hadn’t insisted that by changing places with you I’d be really helping the government, I couldn’t allow you to do it. As it is, I feel I’m cowardly to go through with it—”

“Why, you’re nothing of the sort,” Dorothy protested. While Janet talked and they both undressed, she watched her cousin’s mannerisms, storing away in her memory, for future use, every gesture, and inflection of the voice so like her own.

“Who’s who?” she giggled, and now her tone was softer, an exact duplication of Janet’s manner of speaking.

Her cousin smiled. “In our undies,” she admitted, “even I am beginning to wonder if I’m not seeing double and talking to myself. How about shoes and stockings, Dorothy?”

“Chuck ’em over, Janet, we’d better do it up right. I sp’ose most of your things are packed in that wardrobe trunk over there?”

“Yes. I packed it this afternoon. You’ll find some handkerchiefs and gloves in the top bureau drawer. I left the trunk open on purpose. When Mr. Lawson comes, you might be putting them in—it would help to make things natural.”

“Right you are—that’s a good idea.”

“My arctics and my hat and coat are in the closet. Your coat is much better looking than mine. It’s a shame to take it from you.”

“What’s a coat between cousins who love each other?” laughed Dorothy and put on Janet’s dress.

A few minutes later, the change of clothing had been made, and the girls regarded each other in awed wonder.

“I’ll bet,” Dorothy declared, “that when Howard sees you he’ll think I’ve come back again.”

Janet blushed. “Well, he’ll soon find out different. But it’s a shame to leave you here, darling. If there were only some other way!”

“But there isn’t. So cut along now, and just remember that this kind of thing is my stuff—I love it.”

“Some day I’ll make it up to you—if I ever can!”

Dorothy hesitated for a moment, then smiled. “You can do it tonight, if you want to.”

“Why—what do you mean?”

“Just follow any suggestions that Mr. Sanborn may make.”

“But, what does that—you’re hiding something from me!”

“Perhaps I am.”

“What is it?”

“Never mind, now.”

“But, Dorothy—”

“No time for that, Janet. Get into that swing arrangement with your back to the window.”

“All right, but kiss me goodbye, first.”

They held each other close for a second. Then as Janet took her place on the seat attached to the steel cable, Dorothy switched off the light.

“I’ll—I’ll do as you ask, I mean, about Mr. Sanborn,” whispered Janet.

“Thanks, darling, I—” began Dorothy, her hand on the window sash ready to raise it. Then suddenly she stopped.

Somebody was unlocking the door into the hall.