Set in 1936 the novel follows Nicky Marlow, a young unemployed engineer, who takes a job in Italy for a British munitions company. When Nicky arrives in Milan he discovers that his predecessor had met an unfortunate end when he was the victim of a hit and run, but Marlow soon finds out that the accident was no accident, and then finds himself courted both by the German and Russian secret services. But when the OVRA, the Italian equivalent of the Gestapo, enter the plot life for Nicky will start to get a whole lot more dangerous.
It's quite simply one of the best spy thrillers I've ever read, and its influence on subsequent novelists and film writers is evident. Everyone from Graham Greene to Alan Furst, John Le Carre, and David Downing follow in Ambler's footsteps, as do the writers of Casablanca, and Alfred Hitchcock. Film noir is deeply rooted in Ambler too. Cause for alarm is quite simply brilliant. Ambler's characterisation is superb, there's a wonderfully filmic quality to it that makes his prose come to life. His villains are over the top but none the less villainous for that - General Vagas, the nasty Nazi, just yearns to be played by Sydney Greenstreet, while the Communist spy, Zaleshoff, is immensely likeable - this could be a younger version of Smiley's Karla, charming, single minded and willing to do anything to get his particular "Joe" to safety. Ambler really made me care for these characters - by the end of the novel I was worrying about Zaleshoff and Tamara - would they survive the purges that would inevitably follow the Nazi-Soviet pact of a few years later?
While the set-up of the story is excellent, and Marlow is a great narrator, where the novel really comes to life is in the latter half as Zaleshoff and Marlow attempt to escape the clutches of the OVRA. It was here that I felt the Hitchcock connection with common themes of flight across country, and the odd asides with unusual characters. It had much in common with Hitchcock's later Saboteur, and is undoubtedly significant for every tale since of a spy on the run. Ambler may have been influenced by Buchan here, but he turns it into a modern tale that is very much his own.
What I found most chilling however was its relevance to life today. I had never fully realised before that in the run-up to the Second World War Britain had been supplying arms to Fascist dictatorships. Some of which were probably used in Spain and Ethiopia, some may have even ended up being used against Allied forces. Perhaps it should have come as no surprise that selling arms to less than respectable regimes has a long history, but Ambler's tale is also a salutary lesson - in the world of arms dealing it is wise to choose your friends and customers extremely carefully.
For an extraordinary thriller - a great story with brilliant writing, thought provoking and enthralling, you couldn't do better than read Cause for alarm.