The Night Caller (1965)

Starring John Saxon, Maurice Denham, Patricia Haines, Alfred Burke, Warren Mitchell
Directed by John Gilling
(actor & director credits courtesy IMDB.com)

A team of scientists investigate an alien sphere that descended from outer space, and soon discover it has brought a mysterious creature to Earth.

A suspenseful sci-fi chiller from director John Gilling, this film has only limited special effects but you don't notice, as Gilling tantalizes us with glimpses of the alien and leaves the rest to our imagination.  Good performances all around and subtle touches of humor are also to the picture's credit, with the one wrong note being a somewhat cheesy pop song played over the opening credits that doesn't fit with the rest of the film.  Although the payoff in the film's closing scenes is somewhat of a letdown as Gilling reveals he has tricked us a little bit, all in all, it's an entertaining sci-fi mystery which makes the most of its budget.