The last of the Richard Hannay novels - although he is mentioned in passing in Sick Heart River - this is an entertaining thriller with an evocative title and some good moments. Hannay is oddly passive in the tale, although it's from his POV and it is he who starts it off - in South Africa back in the day he helped out an exotic Scandinavian who was in trouble with some shady characters (cue a flashback action scene where we get to meet Peter Pienaar again - which made me think if Hannay had lived long enough he might have produced an H Rider Haggard style series of prequel adventures of Hannay in Africa), and in the present day he's called in to help out the Scandinavian's wealthy son.
I wish the baddies had gone after Hannay rather than some Scandinavian we'd never met. There are some exciting action scenes but few involve Hannay - one where Hannay's mate, some guy called Lombard (I'm surprised Buchan didn't bring in Pallister-Years or Leithen or someone else... wasn't his universe of Hannay chums wide enough?) rescues the Scandinavian's daughter from boarding school, one where Hannay's kid and the daughter get caught by the baddies and wind up on a boat, an undercover plot where Sandy becomes one of the bad guys, a finale where the Scandinavian goes bonkers and overpowers the head baddy. It's a shame Hannay couldn't have done these things (if they ever adapted this for TV surely that's what they should do).
There's a rivalry between Sandy and the head baddy which isn't developed enough (he sets up a potentially great gang of villains but doesn't do enough with them), some evocative descriptions of the North, Buchan clearly has a culture crush on nordic life with his constant references to the Scandinavian characters in Norse terms. It's fun to have Hannay's son Peter John along on the journey although Mary is a little dim to let him go.