Powerful as he was and with his prisoner at a disadvantage, Foyle found it all he could do to maintain his hold until his companions broke through to his help. Even then it was no easy task, and the fight raged over the tiny cabin with the police hanging on to their prisoner like dogs to a wounded bear. No one spoke a word; there was only the quick panting of struggling men, the shuffling of their footsteps, and now and again a sharp crash as some piece of furniture overturned. Their very numbers handicapped the police in that confined space. Hands sometimes tore at Foyle, sometimes at the prisoner. The superintendent hung on with the tenacity of a bulldog, until a sudden lurch against the side brought his head sharply in contact with the boarding. Half dazed, he involuntarily relaxed his grip. The prisoner tore himself away and struck out viciously. A man fell heavily. For the fraction of a second a shadowy figure was indistinctly outlined in the doorway. Almost simultaneously Foyle, Green, and Wrington flung themselves in pursuit. They were too late. A soft splash told that the man had taken the only possible avenue of escape.

"Look lively with those boats. He's gone overboard," yelled Wrington. "Light up and get close in to the bank."

With the alacrity of men well used to sudden emergencies those detectives in the boats were at work on the word. One darted to cut off retreat to the northern bank, though the forbidding parapet of the Tower made it impossible for any man to land for a hundred yards or more. The other cruised cautiously among the strings of barges, watching for any attempt to land on one of them.

The superintendent had dashed to the stern of the barge and dropped into a small dinghy tethered there. At his word the others came running, and with Wrington at the oars they also crept about in determined search.

"It's hopeless," growled Green, in an undertone. "On a night like this we might as well look for a needle in a haystack."

"We won't give up yet, anyway," retorted Foyle, and there was an unwonted irritability in his tone. "We've mucked it badly enough, but I'm not going to fling it up while there's a sporting chance of finding him. Do you think he'll be able to swim across the river, Wrington?"

"It would need a good man to do it in his clothes. The tide's running pretty strong. More likely he's let himself drop down below the bridge, and will try to pull himself aboard one of these craft."

Heldon Foyle rubbed his chin. Every moment their chances of catching the fugitive lessened. In the darkness, which the lights from the bridge and from adjacent boats only made more involved, there was little hope of finding the man they wanted. He had not been seen from the moment of the first plunge, and there were a score of places on which he might have taken refuge, and where, now that he was warned, he could dodge the searchers. He might have committed suicide, it was true, but somehow Foyle did not think that likely.

For two hours the search continued, and then Foyle, chilled to the bone, decided that it was hopeless. Wrington hailed the other boats, and the detectives returned to the barge. A light thrown into the tiny cabin disclosed amid the disorder an open kit-bag full of linen. Green pulled out the top shirt and felt its texture between thumb and finger. Then he pointed to the name of a West-end maker on the collar.

"Yes, it's hardly the kind of thing a barge watchman would wear," commented Foyle. "We'd better take the bag along, and you can go through it at your leisure. The laundry marks will tell whose they are. You had better stop here, Wrington, and take charge. Find out whom the barge belongs to, and make what inquiries you can. Better have it thoroughly searched, and report to me in the morning. Use your discretion in detaining any one who comes aboard."

One of the motor-boats took Foyle and Green back to Scotland Yard. Both were glum and silent: Foyle because his plan had miscarried at the very moment that he had reached the keystone of the problem; Green because it was his natural habit. It was easy enough to realise now that the whole question was one of light. Had some one thought to strike a match while the struggle was going on there would have been no confusion, and the man would have been unable to get away.

Nor did the news that awaited Foyle at his office tend to make him more pleased with the progress of the investigation. A telephone message had come through the chief of the Liverpool detective force—

"Man found drugged in first-class compartment of express from London, bears warrant card and other documents identifying him as Inspector Robert Blake, C.I.D., London. Is now under care of our surgeon, and has not yet recovered consciousness. In no danger. He travelled from London with a woman fashionably dressed, dark hair, dark blue eyes. Am now endeavouring to find her. Can you suggest any steps we can take?"

Foyle banged his fist viciously on his desk. "There! We're not the only people who have made blunders to-day, Green. Look at that. Wire to them a full description of this woman Petrovska, and tell 'em to detain her if they come across her. We charge her with administering a noxious drug, and that'll hold her safe till we get the business cleared up. If she's trying to slip out of the country, they're pretty safe to get her in one of the liners. Wire over our men at Liverpool to the same effect."

Green slipped away. In a little he returned with a slip of paper in his hand. "Wire's gone to Liverpool. I've drafted this out for Mr. Jerrold, if you'll just look at it. I promised him he should know anything there was to tell."

The sheet of paper read—

"In connection with the investigation into the murder of Mr. Robert Grell, Superintendent Heldon Foyle, accompanied by Chief Detective-Inspector Green, Divisional Detective-Inspector Wrington, and other detectives, examined the body of a man found in the river, whom it was supposed might be the man Goldenburg, for whom search is being made. The police are of the opinion that the drowned man is not Goldenburg."

A light of amusement twinkled in Foyle's blue eyes.

"Don't you think he'll discover that to be a deliberate lie, Mr. Green?"

"Well," said Green doggedly, "we can't tell him what has happened, and we've got to satisfy him somehow. I promised to let him know something, and it's true that a body has been found. I asked Wrington. And it's true that it's not Goldenburg."

"Oh, all right, let it go. You'd better arrange the laundry inquiry first thing in the morning. Now let me alone. I want to think."