With The Dalek Revenge and Virus, Treasure Trail is the last of a trilogy of stories in which the (unseen) Time Lords send the Fourth Doctor and Sarah Jane Smith on various missions by taking control of the TARDIS.
At the time of its release, it was only the third Doctor Who story to be set during World War II, following its TV Action predecessors Timebenders and Who is the Stranger. Whereas those two stories took place in Nazi-occupied France, Treasure Trail was — and remains — unique in that it took place late in the war, about a month after the Battle of Monte Cassino, in a northern Italian village inhabited by partisans. Of the many glimpses of World War II provided by Doctor Who in the ensuing decades, Treasure Trail may be the only one set amongst the Italian resistance.
The Time Lords send the Fourth Doctor and Sarah-Jane on another mission without clear instructions. They find themselves under Nazi aircraft fire almost immediately upon disembarking the TARDIS. The Doctor's people have dumped them near the northern Italian town of Borosini in the summer of 1944.
Suspected by the local villagers of being Nazi spies, they are brought before the town's priest, Father Antonio. The Doctor convinces the priest they are English, using the writing on the TARDIS' police box exterior as proof. Any doubt about the pair's identity, however, is far less significant than the fact that Goering's Nazis are entering the village. It seems they are after whatever artistic treasures they can find.
They storm into the church, and Antonio shows them the Raphael hanging in the knave. Impressed, Lieutenant Schuler sends word of the painting up the Nazi chain of command. Meanwhile, the villagers fear that the Nazis will just steal their art as they've already done elsewhere in Europe. The Doctor offers his aid and wins Antonio's trust by bringing him forward in time to 1976, so he can see the rebuilt Monte Cassino monastery.
Giovanni, a local partisan who has given the Doctor and Sarah a hard time, confirms that there's a massive shipment of stolen art soon to pass through by train. The Doctor proposes to blow the line. They do this, retrieve all the stolen art via a mule trail, and bring it all back to the TARDIS ahead of the Nazis. The Time Lords send the TARDIS to April 1948, where the Doctor offloads the art. To the Italian press, it seems as though the art has magically reappeared. Only Antonio and Giovanni in Borosini knows it's not magic, but it's a secret they vow to take to their graves.
- Fourth Doctor
- Sarah Jane Smith
- Father Antonio
- Lieutenant Schuler
- Major Lunz
- The Doctor uses a lateral transmitter to right the TARDIS from being sideways to upright and to summon it to him and Sarah-Jane.
- This story makes no significant references to other DWU fiction, although it does follow on from The Dalek Revenge and Virus, with the TARDIS still under the control of the Time Lords. From the Doctor and Sarah's perspective, the events of Hubert's Folly take place immediately after.
- It is never explained why the Time Lords deem the Italian treasures important enough to send the Doctor to save them. However, in the later audio story, Fallen Angels, the Fifth Doctor refers to the works of Raphael as a fixed point in time. Another audio story, Operation: Hellfire, shows that the Time Lords have sent the Doctor on a mission during the Second World War once before.
- No exact date is given in-universe as to when most of the story takes place, though it does specify the summer of 1944. If real-life dates apply, one month after the end of the Battle of Monte Cassino would set the story in June, after the capture of Rome.
- The TARDIS is still under the control of the Time Lords. (COMIC: The Dalek Revenge, Virus)
- The Eleventh Doctor again used the writing on the TARDIS' police box exterior to prove that he was from London when he met Adolf Hitler in Berlin in 1938. (TV: Let's Kill Killer)