One glance at the foaming bar where the water gleamed silvery white under the beams of the concentrated searchlights showed him that the plan was a desperate one. A deviation of half a cable's length to port or starboard would be fatal even to the _Olive Branch_, for no vessel could run aground on those deadly shoals and hope to survive. Suddenly, as if by the touch of a magic hand, the searchlights vanished, leaving only a black expanse of storm-tossed waters. Captain Brookes had made use of the Z-rays. Slowly the anchor came home from its muddy bed, the engine-room telegraph signalled full speed ahead, and at her utmost possible speed the _Olive Branch_ dashed towards the bar, every revolution of her propellers bringing her nearer the alert yet mystified British squadron. She was running the gauntlet. Perils unseen awaited her ahead and on either hand. Another five minutes would decide her fate. _(Another long instalment of this splendid serial next month.)_ [Illustration: fourth instalment] BY PERCY F. WESTERMAN Author of "A Lad of Grit," etc. _ILLUSTRATED BY E. S. HODGSON_ *Synopsis* GERALD TREGARTHEN, sub-lieutenant of H.M.S. _Calder_, being on leave, sails from Poole with his old school chum Jack Stockton on board the latter's yacht _Playmate_. In mid-Channel the yacht is run down; the two friends are rescued, and find themselves on board a mysterious cruiser--the Olive Branch--commanded by Captain Brookes. Finding that Tregarthen is a British naval officer, Captain Brookes announces his intention of keeping him on board, and, after due deliberation, Gerald decides to fall in with the captain's plans, as far as his sense of loyalty will permit. Tregarthen is initiated into the secrets of the _Olive Branch_, including that of the deadly ZZ-rays--an irresistible charge of electricity whereby the destruction of a hostile ship can be made at will. Captain Brookes also explains that by the power at his command he hopes to make war so terrible that no nation will venture to declare war; thus universal peace will be assured. During the voyage south Schneider, the ship's scientist, deserts, taking with him some important plans. He is found on board a German "tramp," and is brought back to the _Olive Branch_, which when this action is reported is branded as a pirate. Hostilities break out between Chili and Peru, and Captain Brookes determines to intervene. The _Olive Branch_ is damaged by a mine, and puts into a Chilian harbour for repairs; but while in dock it is trapped by a British squadron demanding its surrender by daybreak. Captain Brookes is handicapped by a vow never to fire on a British vessel. At midnight when the damage to his ship has been repaired, he makes use of his Z-rays to extinguish the searchlights of the British squadron. Then the _Olive Branch_ starts forward at full speed. [Illustration: chapter XV] CHAPTER XV A ONE-SIDED ENGAGEMENT