"Right-o," rejoined Ainslie. "And just kick over the oiler. Here's a link that wants a drop of oil pretty badly. Thanks, old thing."

The Sub was about to attend to what appeared to be a stiff link in the dummy deckgear release, when a cry came from for'ard:

"Submarine two points on the starboard bow, sir!"

At a distance of two miles in the direction indicated lay a U-boat motionless, with her deck just awash. Telescopes and binoculars were brought to bear upon her.

"That's not the bird I want," declared Morpeth. "She's one of the ordinary submarine mine-layers. We'll sheer off. No sprat to catch a mackerel for me!"

Q 171 turned eight points to port. Expecting at any moment to be challenged by the U-boat, Morpeth gave a curt order to the signalman. The latter toggled the soi-disant U 251's signal numbers to the halliards and stood by.

"They don't keep a sharp look-out," remarked Wakefield. "If we can spot them lying awash, surely they've twigged us by now."

"Just back from a cruise, I expect," surmised the R.N.R. officer. "And jolly glad to be back out of it, so they're holding on to the slack."

"Where's the other one, then?" inquired Wakefield. "There were two expected."

"She's neither of 'em," explained Morpeth. "Sort of stray cat coming home. The ones expected to meet the submarine-cruisers are big ones—three hundred feet or thereabouts. This one's not more'n a couple of hundred. I'd slip a tinfish into her with the greatest of pleasure, only that would spoil the proper stunt. Au revoir, Fritz!"