Straight in front of him, looking over the house tops, he could see the gleam of water.  It was a reservoir, he decided.  Probably it constituted the water supply for a considerable section.  And then, as he looked, he saw a flash —­ saw a great column of water rise in the air, and descend, like pictures of a cloudburst.  A moment after the explosion, he heard a dull roar.  And after the roar another sound.  He saw the water fade out and disappear, and it was a moment before he realized what was happening.  The reservoir had been blown up!  And that meant more than the danger and the discomfort of an interrupted water supply.  It meant an immediate catastrophe —­ the flooding of all the streets nearby.  In England, as he knew, such reservoirs were higher than the surrounding country, as a rule.  They were contained within high walls, and, after a rainy summer, such as this had been, would be full to overflowing.  He was hammering at his door in a moment, and a sleepy policeman, aroused by the sudden alarm, flung it open as he passed on his way to the floor below.

Harry rushed down, and mingled, unnoticed, with the policemen who had been off duty, but summoned now to deal with this disaster.  The inspector who had received him paid no attention to him at all.

“Out with you, men!” he cried.  “There’ll be trouble over this —­ no telling but what people may be drowned.  Double quick, now!”

They rushed out, under command of a sergeant.  The inspector stayed behind, and now he looked at Harry.

“Hullo!” he said.  “How did you get out?”

“I want to help!” said Harry, inspired.  “I haven’t done anything really wrong, have I?  Oughtn’t I be allowed to do whatever I can, now that something like this has happened?”

“Go along with you!” said the inspector.  “All right!  But you’d better come back —­ because we’ve got your motorcycle, and we’ll keep that until you come back for it.”

But it made little difference to Harry that he was, so to speak, out on bail.  The great thing was that he was free.  He rushed out, but he didn’t make for the scene of the disaster to the reservoir, caused, as he had guessed, by some spy.  All the town was pouring out now, and the streets were full of people making for the place where the explosion had occurred.  It was quite easy for Harry to slip through them and make for London.  He did not try to get his cycle.  But before he had gone very far he over took a motor lorry that had broken down.  He pitched in and helped with the slight repairs it needed, and the driver invited him to ride along with him.

“Taking in provisions for the troops, I am,” he said.  “If you’re going to Lunnon, you might as well ride along with me.  Eh, Tommy?”

His question was addressed to a sleepy private, who was nodding on the seat beside die driver.  He started now, and looked at Harry.

“All aboard!” he said, with a sleepy chuckle.  “More the merrier, say I!  Up all night —­ that’s what I’ve been!  Fine sort of war this is?  Do I see any fightin’?  I do not!  I’m a bloomin’ chaperone for cabbages and cauliflowers and turnips, bless their little hearts!”