Wallace is the head of the British Secret Service, who discovers, on returning from the States, that some secret papers have gone missing, and the spy who's been sent to retrieve them has also gone walkabout. As though it wasn't bad enough that the Russians and the Germans are trying to buy British military plans, the head of the French Secret Service turns up in London with a plea for help. Can the British save the day?
It's a fun tale, often unintentionally funny (Wallace's 12 year old son spends lots of time having his head patted by well-meaning adults, when they're not tucking him up in bed, that is. Despite this he still manages to save his father's life, and (quite literally) dodges a bullet). Villains are either foreign, disabled or both. And yes, as you'll have realised, the mores of the day were pretty weird.
However having slated it, I've got to say that it's quite hard not to enjoy it - in a guilty pleasures sort of way. The story jogs along at a ripping pace, and (most importantly) it soon becomes obvious that Wilson was an enormous influence on later and rather better writers. Without Wilson there would have been no Ian Fleming - from attractive but deadly women to a killer dwarf, they were all in Wilson's work first. There's the arch-villain determined to destabilise governments and take over the world, there are gadgets, and a hero, who strikes fear into baddies' hearts.
To a lesser extent Wilson also influenced Eric Ambler, in the way in which he paced his novels, and of course Len Deighton via Ian Fleming.
It's a ripping yarn, and hard not to enjoy, even if it's occasionally not exactly PC. A story could quite easily have been written about Alexander Wilson himself - writer, lecturer, spy and philanderer, that is, in its way even more extraordinary than the tale of Wallace. A fascinating souvenir of a different era.