"That ship must be up to something extremely desperate to dare to fire on a British 'blimp'!" exclaimed Dave Darrin. "But we're getting close, and soon ought to know what we have to tackle!" CHAPTER XVIII STRIKING A REAL SURPRISE "ARE we heading straight course?" was Dave's next question through the air. "You're going straight," came the cheering information. "Found out your hurt?" "Yes; gas-bag intact, and we've withdrawn out of easy range. One motor damaged more than we can repair in air. Can limp home, however." "Leave the steamship to me," Darrin wirelessed back. Inside of another minute and a half, Darrin made out the mast-tops of the stranger sticking up from the fringe of haze as the cloudy, reddish curtain shifted. If Dave had sighted his intended prey, so had the stranger caught sight of the destroyer. The steamship cut a wide circle and turned tail. "He's going at nineteen knots, we judge," came the radio report from the "blimp." "That won't do him any good!" was the laconic answer that Darrin returned, this time in plain English instead of code. The lower masts, the stack and then the hull of the stranger became visible as Darrin gained on him. Bang! A shell struck the water ahead of the stranger, the war-ship's world-wide signal to halt. Instead, the stranger appeared to be trying to crowd on more speed. "Give him one in the stern-post," Darrin ordered. The shell fell just a few feet short. The third one landed on the after-part of the stranger's deck-house. And now there went fluttering up the top of the destroyer's mast the international code signal: "Stop or we'll sink you!" It took another shell, this one crashing through the stern of the stranger, to convince her skipper that the destroyer was in deadly earnest. By this time the "Grigsby" was a bare half-mile away, and going fast. "We're bringing to bear on you to blow you out of the water," Darrin signalled this time. "Will you stop?" If he had made any plan to die fighting the fleeing skipper must have lost his nerve at that point, for he suddenly swung his bow around, reduced speed and moved ahead at mere steerage-way. "Call Ensign Peters to clear away a launch with an armed crew," Darrin directed. "I will accompany him, for I must see what reason that craft had for firing on a British dirigible." On either bow of the strange steamship was painted the national flag of the same neutral nation to which the "Olga" had appeared to belong. She flew no bunting. "Stand by to receive boarding party," a signalman on the "Grigsby's" bridge wigwagged as the launch started toward the water. The two craft lay now not more than five hundred yards apart. Across the water sped the fast power launch and came up alongside of the unknown steamship, which displayed no name. Not a human being was now visible on her deck. An undersized watch officer had appeared on the bridge, but he now vanished.