In the latest Big Finish main range release, the sixth Doctor (Colin Baker) is travelling alone when he arrives in the middle of a supernatural mystery. The setting is the digging of the Thames Tunnel, London, 1828 and in Chris Chapman’s wonderful story the Doctor makes the acquaintance of Isambard Kingdom Brunel (Jam MacCallum), his father Marc (Christopher Fairbank) and their maid Flo (Becky Wright). What seems to be a rare pure historical (albeit with a strange blue female ghost) turns into much more.

The Doctor agrees to help Marc Brunel determine the cause of hauntings, slowing down his work. At this time young Isambard has yet to make a name for himself (he’s only 22) or to become the foremost engineer of his age. Imagine were he to see the inside of the TARDIS! We also meet  several down to earth (perhaps beneath?) workers, the upper-class investors in the project and even an appearance by a band!

There’s plenty of historical detail, a guide on tunnelling and ghostly happenings, all of which are turned on their head in the second disc when another realm enters the picture. These are far from standard fare, instead of being all hands to the invasion, they have a certain interest in London and the full story is laid out in careful stages, giving plenty of time for the various characters to develop. The climax is built in layers, and even though we have an established history (we know Isambard survives, even if we are less familiar with his father), events still need to work themselves out.

At times the story is dark, funny and downright charming. As events progress, Isambard needs to find his feet and think about stepping out from under his father’s shadow. Fortunately, he is not alone at the key moments.

There’s plenty to like in this two-disc adventure, and it proves that the sixth Doctor is fully capable of operating without his normal companions, tough does, perhaps, set up some of the inhabitants of the story as his assistants. Delightful stuff!