This is the film version of a very good thriller serial written by Francis Durbridge and televised by the BBC in 1955. The original was excellent, but in my opinion, the transfer to the big screen has not worked well. This film version disappointed me. The police in Durbridge serials often used the main suspect as a stalking horse to reveal the actual miscreants, and an essential part of the enjoyment was the main suspect's growing bafflement until the denouement. In this film, it is hardly visible. Additionally, the cliff-hangers that made the serial such a pleasure are almost imperceptible here. What this leaves is a very run-of-the-mill whodunnit, which I found adequate, but no more than that. Transferring Durbridge's serials to a continuous format _can_ be done properly, as witnessed by the DVD "Melissa" (from the serial "My Wife Melissa), but that has not happened here.