He dashed in pursuit, but it was too late.  Being war time, the decks were of course in darkness, and the man, whoever he was, disappeared—­probably down the forward hatch.

Ken came back to Burney.

‘No good,’ he said vexedly.  ‘The beggar was too quick for me.’

‘Then there was some one there?’

‘You bet.  I saw him bolt.’

‘Any notion who it was?’

Ken hesitated a moment.

‘I’m not sure,’ he answered in a low voice, ’but I’ve got my suspicions.  I think it was Kemp.’

‘What—­that steward?’

‘Yes, the chap who looks after the baths.’

‘My word, I wouldn’t wonder,’ said Burney thoughtfully.  ’He’s an ugly looking varmint.  But why should he be spying on you?’

’Haven’t a notion.  But I’ve spotted him watching me more than once since we left Alexandria.  I’m going to keep my eye on him pretty closely the rest of the way.’

’Not much time left, old son.  They say we’ll be in Mudros Bay to-morrow morning.’

’Yes, I heard that.  Which reminds me.  I’m going down to get a warm bath.  It may be the last chance for some time to come.’

This time Ken Carrington said good-night in earnest, and went below.

It was early for turning in, and nearly all of the troops aboard were still on the mess deck.  Ken got his things from his bag and went down the passage to the bathroom.  The ‘Cardigan Castle’ had been a swagger liner until she was impounded by Government to act as troopship, and she was provided with splendid bathrooms.

Carrington opened the door quietly, and was feeling for the switch of the electric, when he noticed, to his great surprise, that a port hole opposite was open.

Needless to say, this was absolutely forbidden.  In war time a ship shows no lights at all, and it is a fixed rule that everything below must be kept closed and curtained.

Before he could recover from his first surprise he got a second shock.  A tiny pencil of light—­just a single beam, no more than a few inches in diameter—­struck through the darkness and formed a small luminous circle upon the white-painted wall above his head.

It only lasted an instant, then a dark figure rose between him and the open port, and instantly the beam was intercepted, and all was dark as before.

Through the gloom he vaguely saw the arm of the man who stood in front of the port raised to a level with his head, while his hand moved rapidly.

Instantly he knew what was happening.  This man was signalling.  Carrington had heard of the German signalling lamp which, by means of ingeniously arranged lenses, throws one tiny ray which can be caught and flung back by a specially constructed mirror.  That was what was happening before his very eyes.  A glow of rage sent the blood boiling through his veins, and forgetting all about the switch he sprang forward.

As ill luck had it, there was a wooden grating in the middle of the cement floor.  In the darkness, he failed to see this, and catching his toe, stumbled and fell with a crash on hands and knees.