Paranoiac (1963), directed by Freddie Francis.
A wealthy young woman from a country house begins getting glimpses of her brother, dead for eight years. Her mental state is fragile at best: is someone trying to gaslight her?
But then he rescues her from drowning when she jumps from a sea cliff and takes her home. He does indeed seem to be the long-dead brother. An inheritance is due soon: do we suspect an impostor? How many twists and turns until we get to the truth?
Even at a short 80 minutes it is not an intense thriller, but the performances are good and the scope ratio black-and-white imagery always fun to watch. It is made with the typical Hammer skill and high production values.
Janette Scott fan club! She gets top billing; how often did that happen?
Pretty-eyed Oliver Reed is the drunken, dangerous and probably mental other brother. An early significant part for him; he'd been doing uncredited bits for a while.
Loosely based on Josephine Tey's novel Brat Farrar.
Available on Blu-ray with an image that is often quite good. Hammer's The Kiss of the Vampire (1963) is on the same disc; it's not very thrilling.