Originally thought to be the last Sapphire & Steel play that Big Finish would produce, the overall tone of The Mystery of the Missing Hour is “we have nothing to lose, so let’s do something completely different”.

Instead of the famous theme and Sapphire giving exposition, bombastic, only faintly familiar music ushers in Colin Baker’s melodramatic narration of the events in the Cairo Hilton, December 3rd, 1926. It is 8pm. Soon a body will be discovered, of someone who left the group only a few minutes before. But the doctor will determine that she had somehow been killed an hour before discovery – the missing hour of the title.

Fortunately for the guests, a pair of very familiar voices are introduced as Shuffle and Sixpence, “the most famous amateur detectives in London.” Although an obvious parody of Christie, they act more like characters in a Thin Man movie – Shuffle repeatedly talks about how wonderful his lovely wife is, while Sixpence sums up their style with “Find the murderer, open the champagne.”

It’s a cold, giddy thing to say, but everyone in this story is cold and giddy – two-dimensional characterisations rather than three-dimensional characters. Even the production values are off, with actors self-correcting their lines. And Shuffle and Sixpence keep getting strange messages with references to all kinds of metals – gold, silver, steel…

There’s more to this audio than just the broad outlines of a murder mystery, but the story won’t move beyond the Cairo Hilton until well in the second disc – terribly late for Sapphire and Steel to try to save the day. There’s a twist ending, of course, although anyone familiar with the history of the show will be expecting it, while listeners will have it figured out several minutes before it happens.

The Mystery of the Missing Hour is audaciously different, worth a listen just for the change of pace from the standard Sapphire & Steel story. How much you enjoy it is going to depend on how much you enjoy the kind of very broad, very dated parody which takes much of the airtime, although Colin Baker fans will enjoy hearing him do a full range of characters that have nothing to do with the Sixth Doctor.

The Mystery of the Missing Hour (by Joseph Lidster; starring David Warner, Susannah Harker) was released by Big Finish Productions in June 2007.