Impossible to detonate by combustion, friction, or the application of heat, the explosive was perfectly safe to handle until the temperature fell below -5° C. The moment the mercury dropped to that point the explosive would simultaneously and spontaneously act. In his attempt to induce Fordyce to convey the "diamonds" to Russia the German agent was employing a double-barrelled weapon. If the stuff did get to Petrograd well and good. If, on the other hand, the temperature on board the submarine should fall below -5° C. while running awash towards the port of Cronstadt, it meant utter annihilation to R19 and terrific damage to everything within a mile of the source of the explosion. And, confident in his ability to make use of Flirt as the deciding factor, von Verbrennungsraum duly applied for and obtained a summons against Noel Fordyce. CHAPTER III The Sub's Stratagem Ernst von Verbrennungsraum had not taken into account one of Noel Fordyce's characteristics--that of grim, almost obstinate determination. Under the mistaken impression that, for the sake of his pet, the Sub would agree to his terms, the Secret Service agent applied for and obtained a summons. "I'll fight him while I have a penny left to call my own," declared Fordyce, and with this laudable intention he engaged the best solicitor in Otherport. The German could not now back out without loss of dignity as a respected member of the Otherport Town Council. He had to proceed with the case, unless Fordyce capitulated. The morning of the day fixed for the hearing came round. Noel Fordyce, in uniform, made his way towards the Town Hall. Flirt was safely under lock and key. An hour would decide whether she was to live or die. The young officer had not reached the end of the road when an Irish terrier bounded up to him. It was Nell, Colonel Richardson's animal and Flirt's mother, a quiet, affectionate and absolutely inoffensive little beast. Flirt did not inherit her one bad trait from her mother. "Go back, Nell," ordered Noel. "Home! I can't take you for a stroll this morning." The dog, for once in a way, took no notice of the command. After several vain attempts to send her back, Fordyce gave it up as a bad job, and with Nell close at his heels he entered the Town Hall. The police on duty at the door of the court made no attempt to turn the animal off. They naturally but erroneously thought that this was the canine delinquent. While Fordyce was chatting with his solicitor the dog began exploring. Round the well of the court she trotted, wagging her stumpy tail; then, receiving a friendly caress from the bewigged clerk, she proceeded, with scant regard to judicial authority, to the bench itself, where the Great Unpaid gave her a cordial welcome. Just then Councillor Mindiggle appeared. Catching sight of the dog, the spy let himself go with a display of excitability that almost betrayed his Hunnish nationality.