‘If you will come with me,’ continued Dr Tosswill. ‘I will take you to Sir Guy Willard. He was most anxious to be informed as soon as you should arrive.’

We were taken across the camp to a large tent. Dr Tosswill lifted up the flap and we entered. Three men were sitting inside.

‘Monsieur Poirot and Captain Hastings have arrived, Sir Guy,’ said Tosswill.

The youngest of the three men jumped up and came forward to greet us. There was a certain impulsiveness in his manner which reminded me of his mother. He was not nearly so sunburnt as the others, and that fact, coupled with a certain haggardness round the eyes, made him look older than his twenty-two years. He was clearly endeavouring to bear up under a severe mental strain.

He introduced his two companions, Dr Ames, a capable-looking man of thirty-odd, with a touch of greying hair at the temples, and Mr Harper, the secretary, a pleasant lean young man wearing the national insignia of horn-rimmed spectacles.

After a few minutes’ desultory conversation the latter went out, and Dr Tosswill followed him. We were left alone with Sir Guy and Dr Ames.

‘Please ask any questions you want to ask, Monsieur Poirot,’ said Willard. ‘We are utterly dumbfounded at this strange series of disasters, but it isn’t—it can’t be, anything but coincidence.’

There was a nervousness about his manner which rather belied the words. I saw that Poirot was studying him keenly.

‘Your heart is really in this work, Sir Guy?’

‘Rather. No matter what happens, or what comes of it, the work is going on. Make up your mind to that.’

Poirot wheeled round on the other.

‘What have you to say to that, monsieur le docteur?’

‘Well,’ drawled the doctor, ‘I’m not for quitting myself.’

Poirot made one of those expressive grimaces of his.

‘Then, évidemment, we must find out just how we stand. When did Mr Schneider’s death take place?’

‘Three days ago.’

‘You are sure it was tetanus?’

‘Dead sure.’

‘It couldn’t have been a case of strychnine poisoning, for instance?’

‘No, Monsieur Poirot, I see what you’re getting at. But it was a clear case of tetanus.’

‘Did you not inject anti-serum?’

‘Certainly we did,’ said the doctor drily. ‘Every conceivable thing that could be done was tried.’

‘Had you the anti-serum with you?’

‘No. We procured it from Cairo.’

‘Have there been any other cases of tetanus in the camp?’

‘No, not one.’

‘Are you certain that the death of Mr Bleibner was not due to tetanus?’

‘Absolutely plumb certain. He had a scratch upon his thumb which became poisoned, and septicaemia set in. It sounds pretty much the same to a layman, I dare say, but the two things are entirely different.’

‘Then we have four deaths—all totally dissimilar, one heart failure, one blood poisoning, one suicide and one tetanus.’

‘Exactly, Monsieur Poirot.’

‘Are you certain that there is nothing which might link the four together?’

‘I don’t quite understand you?’