‘Doubtful. Not impossible. You see, with her as the only member of the house who had a chance of getting into this workroom I thought quite a lot about Madam. She might have got a key for herself when she had the Yale lock put on the door for the young gentlemen. It wasn’t impossible. She had to be considered. And the more she talked about getting rid of enemy agents in this country the more I wondered if she might be one herself. She used to say that we oughtn’t to be afraid to use what was good in Nazi methods: their youth training schemes and fostering of nationalistic ideas, and she used to come down very hard on anything like independent critical thinking. It was all right, of course. Lots of people think that way, all the diehards, you might say. She read a lot of their pre-war books, too. And she didn’t like Jews. She used to say they were parasites. I’d get to thinking about her this way and then I’d kind of come down with a bump and call myself crazy.’

Alleyn asked him if he had anything more tangible to go on and he shook his head mournfully. Nothing. Beyond her curiosity about the young men’s work, and she was by nature curious, there had been nothing. There was, he said, another view to take, and in many ways a more reasonable one. Mrs Rubrick had been appointed to a counter-espionage committee and, in that capacity, may have threatened the success of an agent. She may even have formed suspicions of a member of her household and have given herself away. She was not a discreet woman. This, pushed a little further, might produce a motive for her murder.

‘Yes,’ said Alleyn dryly. ‘That’s why Captain Grace thinks you killed her, you know.’

Markins said with venom that Captain Grace was not immune from suspicion himself. ‘He’s silly enough to do anything,’ he whispered angrily. ‘And what about his background anyway? Heidelberg. He doesn’t look so hot. And what about him being a Nazi sympathizer? I may be dumb but I haven’t overlooked that little point.’

‘You don’t really believe it, though, do you?’ Alleyn asked with a smile.

Markins muttered disconsolately, ‘No brains.’

‘There’s one other point,’ Alleyn said. ‘We’ve got to consider whether this attempt to forward documentary information was the be-all and end-all of the agent’s mission. If, having achieved this object, no more was expected of him, or if he were to forward other information as regards, for instance, Mrs Rubrick’s counter-espionage activities, which is the sort of stuff that needs no documentary evidence. That perennial nuisance, the hidden radio transmitter, would meet the case.’

‘Don’t I know it,’ Markins grumbled. ‘And there’s a sizable range of mountains where it could be cached.’