As plans for D-Day loom large and Department Z work overtime to halt the leak of British secrets to Berlin, three cousins undertake their own covert operation: meeting in a cottage in Guildford to discuss a dark family matter in secret.

As these two seemingly unrelated events collide, the cousins are drawn along a secretive trail that leads to a powerful spy ring. The team faces a race against the clock…infiltrate this tight-knit organisation, or risk devastating consequences.

‘Following closely on the heels of history, and sometimes a little ahead of it, Mr. Creasey and Department Z are busy preventing someone from putting a spoke in the wheels of the Allied invasion of Europe.’ Evening Chronicle

Prepare for Action is the 19th book in the Department Z series, and was originally published in 1942.