Intelligent - and, at the time, X-Rated - sci-fi (written by James Kennaway) which I had always been interested in watching, given its theme and credentials.

Featuring excellent performances by all the main actors (Dirk Bogarde, Mary Ure, John Clements, Michael Bryant and Wendy Craig), fine black-and-white cinematography by Denys Coop and a good score by Georges Auric, the film deals with sensory-deprivation experiments which if over-exposed can render the subject susceptible to brainwashing. The idea is persuasively handled by the script and director Dearden, and actually predates Ken Russell's ALTERED STATES (1980) by almost 20 years!

Still, after an intriguing first hour - with its introduction of suspense elements (where a scientist who has committed suicide is thought to have betrayed secrets to the enemy whilst 'under the influence') and the realistic depiction of the harrowing experiments (hinting at the supernatural), the plot is side-tracked into dealing with the domestic problems of Bogarde and Ure (which are mostly talked about rather than seen!) brought on by his change in personality during his stint in the water-tank - conditioned by Clements' Secret Service man and Bryant's fellow colleague, secretly enamored of his wife.

As such, the treatment is somewhat too highbrow (for the most part, it's made by people not usually associated with this type of film) but it's fascinating - and generally satisfying - all the same.