Often effective British thriller features a tip-top cast(Joan Collins, Peter Cushing, Ralph Bates, Judy Geeson), but suffers from a lack of originality as this is, for the most part, a rehash of similar motifs explored in earlier British horror films like PARANOIAC and NIGHTMARE, which themselves derived from the brilliant French thriller DIABOLIQUE. Still, the good outweighs the bad and there are plenty of nice, genuine jolts.