A further combination of improbable to irrepressible events in which Claude Boster, a lawyer, assigns Henry, his assistant, to watch over Diana, Boster's stepdaughter, threatened by the reprisals of a disgruntled criminal. Henry's surveillance takes him from a hospital, and a nightwatch in a hospital gown, to a black house in the country where- after several attempted and two accomplished murders- the killer is caught. Skittish.