The Sleeping Sentinel (1966)

Doctor Mathieu helps the royalists plot against usurper Napoleon .The assassination will take place in Chalons where Mathieu claims he's got to visit some patients .But the emperor's police has got wind of the attempt.Now their master will spend the night in a small village, in Mathieu's own house. And ,unbeknownst to him, one of his accomplices puts the explosive device in his desirable mansion.