The Wrong Box (1966)

Two elderly brothers Masterman (John Mills) and Joseph Finsbury (Ralph Richardson) are the last surviving members of a tontine, an investment scheme set up many years before, in which the last surviving member stands to receive a fortune. Masterman is attended by his medical student grandson, Michael (Michael Caine), while his greedy cousins Morris (Peter Cook) and John (Dudley Moore) do their best to keep their annoying uncle Joseph alive. Masterman, who hasn't talked to his despised brother in many years, summons Joseph to his "deathbed", intending to kill him so that Michael can get the money.

On the train trip to London, Joseph escapes from his minders, entering a compartment and boring the sole occupant with a litany of trivial facts (something he does with everyone he encounters). The other man later turns out to be the "Bournemouth Strangler". Joseph later leaves to smoke a cigarette leaving his coat behind, which the strangler puts on. The train then crashes head-on into another one coming the other way. In the confusion, Morris and John find the strangler's mutilated body and mistakenly believe it is that of their uncle.

Morris decides to try to hide this long enough for Masterman to pass away. Morris and John put the body in a barrel and have it shipped to their London home, next door to Masterman's residence. However, it is delivered to the Masterman house. Joseph makes his way to London on his own and visits his brother; they quarrel.

Meanwhile, Michael meets and falls in love with Joseph's ward, Julia (Nanette Newman). Things become complicated when Michael discovers the contents of the barrel and, after learning of the dispute between Masterman and Joseph from family butler Peacock (Wilfrid Lawson), assumes that his grandfather has killed his brother. Various misunderstandings and antics result.