As detective Paul Temple turns his hand to writing plays, his leading lady Iris Archer pulls out shortly before the play is due to open and declares that she is heading for France. However, shortly after her disappearance Paul Temple receives a guest at his Scottish holiday home – none other than that of Iris Archer. As the plot thickens a mysterious letter is passed on to Paul Temple by a young man, with explicit instructions to deliver it to John Richmond. Meanwhile, what does the enigmatic Doctor Steiner have to do with events? And more importantly, who is the masked leader operating under the codename Z4? It is up to Paul Temple to unravel the case.