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."