Deadly Nightshade

Emrys Jones is arrested for being an escaped prisoner. He isn't, but when the police finally release him and drop him off at home, the real escapee (played, conveniently enough, by Jones) shows up and takes over the life of the other guy.

But wait! There's more! There's some sort of accident and the usual harrumphing retired colonel and his wife are sequestered on Jones, as is Zena Marshall, who just so happens to be the escaped man's ex-fiancee!

At time it's seems as if about one in five movies involves an actor (or actress) playing identical twins, whether actual twins or doppelgangers. As the film slogs on -- and it does seem to bog down under the steady stream of coincidences -- various plot twists come into operation to make the version of Jones who started out as the bad guy the good guy, and vice versa. However, to be frank, I didn't care.