Most of Big Finish’s audio lines star the original series actors. However, with David McCallum in the US working on NCIS and Joanna Lumley busy working on other projects, David Warner and Susannah Harker have stepped into the titular roles for the Sapphire & Steel range, joined by Big Finish regular Mark Gatiss as Gold.

The British cult show ran for only six “assignments” from 1979 through 1982. A series of so-called elementals (several of whom are not actually named after elements) work as operatives who investigate vaguely-defined “irregularities” – mostly breakdowns in linear time. It is suggested that Time itself is alive and malignant, always attempting to break free. Who assigns operatives and what dimension or planet the characters come from is never explained.

When the very late commuter train is replaced with a steam engine, book dealer and train aficionado Phillip Burgess is happy to step aboard. At first his only companions are the elegantly dressed woman who seems very interested in his book, the abrupt man who keeps asking him questions, and the little girl who keeps singing, “This is a choo-choo train, puffing down the track…”

Every now and then the train makes a stop and takes on more passengers, although the station name can never be seen in the fog. According to Sapphire, each compartment of the train is set in another year. According to Steel, each of the new passengers has the same secret. And according to Phillip Burgess’ new book, everything happening has already been written.

Sapphire and Steel adapts well to the audio medium. The ghost story feel and creep factor rise when not encumbered by special effects that date over time. Limited to two hours and without the leads being able to stare meaningfully and silently into space for much of an episode, the pacing moves steadily.

Harker and Warner are playing the characters as older and more experienced than they seemed on TV. They are a comfortable, established team, confident in their own abilities and each other. Sapphire has become fonder of humanity (rather in the manner of a cherished pet). 20 years of feminism later, she is also more proactive – more likely to argue with Steel and less likely to quietly accept his orders. Steel has become more irascible towards humans – where Sapphire finds them amusing, he finds them a bit disgusting and barely tries to hide it – and he has become more reliant upon Sapphire. But they are still recognisably the characters from TV.

Lyons has thrown in a self-referential in-joke by referencing TV tie-ins. And get used to the “choo-choo” train soundbite; it’s going to show up in quite a few of the sequels. Still, The Passenger is an excellent story – a good extension of the show for its fans, and a solid standalone introduction to the universe to new listeners. Big Finish needed a good start to launch this series, and they knocked it out of the park on the first try.

The Passenger (by Steve Lyons; starring David Warner, Susannah Harker) was released by Big Finish Productions in May 2005.