This is the Big Finish Sapphire and Steel release 3.4, Wall of Darkness, with Susannah Harker as Sapphire and David Warrner as Steel. Written and directed by Nigel Fairs. And once again here's a signed CD cover.
This was the last of the Big Finish Sapphire and Steel stories which we covered back in British Invaders episodes 109 & 110. I sold my CDs after we reviewed them but I bought this one again for a fiver at Big Finish day so I would have something for David Warner and Nigel Fairs to sign. I had not planned to listen to it again but my current Big Finish obsession encouraged me to stick it in the CD player again.
The mysterious investigators find themselves in an abandoned shopping mall, or are they in a top secret bunker miles deep below the surface of the Earth? As ever there seems to be some problem with time and Sapphire and Steel must identify the cause and fix it before they are wiped out of existence.
Wall of Darkness brings together several plot threads that had been slowly evolving through the three series of Big Finish releases. Discussing them would involve spoilers which I am not going to give away here. Suffice it to say that there is more than one simple mystery for Sapphire and Steel to solve. Things get wrapped up, but also set up for a possible sequel (which, at the time of writing, seems unlikely to happen).
Warner and Harker are splendid and I enjoyed listening to this story again, especially as for the first episode I was convinced I had missed this out when listening to the others. Wall of Darkness gets a solid 3 out of 5 mysterious artefacts.