Roger Waterlow is an agent with the British Secret Service.
The time of the first recorded adventure is past the start of the First World War though not yet to the middle. Waterlow has found himself in the Balkans and being in the hottest part of the year, he is most decidedly not happy as he suffers the heat and grime and worse yet, the smell so different from his longed for England.
When he was a young man still in his teens and becoming an officer in the Royal Navy two decades before, he would never have imagined or believed that when war came as it would in 1914, he would not be in the captain's chair on the bridge of a warship. The sea was his destiny, he thought, and that was that.
Then a few years later came the nasty business where as a Lieutenant he was said to be the blame for an unfortunate incident and the court martial that followed quite angered him so instead of taking his lumps and moving on, he "chucked the Navy". He was then certain that he would still reside at sea though this time as the captain of a cargo ship and when the next war came, and one was always coming, he could take part as the master of a "Q" ship (which he explains is a warship decked out as a cargo ship to lure U-boats close enough to take them out).
But then a pal suggested in passing that he meet with an interesting fellow who was on the lookout for enterprising and intelligent men to do some different sort of work. Mr. X was the name that Waterlow used when referring to him and X was someone in a rather important position in the Secret Service directing people doing all manner of clandestine things all over the world.
Waterlow would muse later that had he not liked this chap X so much he would never have taken the short-term job and the short term would not have stretched into many years and Waterlow would have, now that war with Germany and Austria and Turkey was ongoing, that Q ship captaincy. Instead, he was landlocked and still in the spy business and still dealing with the heat and the smell and oh! so very much worse.