Alex Forrester (Whitman) is a mental patient who murdered his wife and has spent the past 10 years inside a British asylum for the criminally insane. But now he feels he's totally rehabilitated. Completely sane. When he's denied parole, Alex decides he doesn't relish the idea of spending any more time behind locked doors.

So one evening, he beats his psychiatrist Dr. Fleming (Mulhare) unconscious, and makes a beeline for the nearby English countryside, hoping to disappear into the woods and foliage.

In the dark of night, Alex comes across an unassuming country mill house inhabited by Molly Thomas (Woodward), a patient wife who's waiting for her husband to return from a business trip abroad.

It's an inviting home and one that Alex is already familiar with: he's watched it for years from the window of his cell in the sanitarium overlooking the valley.

Alex enters the house and takes Molly hostage. Surely, he thinks, this will be a good place to lay low for a few days until the police and asylum authorities have given up the search.

Then he spots it: the body of a dead man, wedged between the blades of the waterwheel, the man's throat slit clean open.

Slowly, Alex comes to doubt his newfound sanity. Who is this murdered guy? Could he have killed him in some sort of mad rage as he made his way out of the sanitarium? And why has the corpse suddenly disappeared? Could there be another dark secret at work here?

Signpost to Murder doesn't betray its roots. Based on a stage play by Monte Doyle, the action feels appropriately confined and claustrophobic. The set design -- the creaking, ever-turning mill wheel, the authentic wooden interiors -- adds a nice touch of theatricality and atmosphere.

The whole thing certainly boasts its own brand of star power: Woodward had won an Oscar for her performance as a woman suffering with a multiple personality disorder in The Three Faces of Eve (1957), while Whitman had appeared in the epic war flick The Longest Day (1962) and had been nominated for his own Academy Award for his turn as a child molester in The Mark (1961).

Unfortunately, Signpost doesn't always live up to its own potential.

After a few strong opening scenes in the asylum (the sequence where Whitman clobbers Mulhare is especially well done), the film takes a detour into the mediocre.

A half-hearted romantic subplot between Molly and Alex never seems to take flight. And despite the cool moment where Alex sees the corpse in the waterwheel, there's not enough palpable tension throughout, either between Molly and Alex, or the movie as a whole. With the climax comes a nice twist revelation, but also a whiff of implausibility. By then it's all too late.

Average all the way around.