Third in the Theatre of Thieves series - I hadn't read the other two but realised it's about a family of thespians who get involved in heists.

This time round, the Fitzglens are asked to find some Russian artefacts which are linked to a very grisly story during the reign of Catherine the Great - stone heads which are the images of murdered children and which also hide an explosive secret. Plus they discover links to their own family history, and the fact that one of their own (a baddie) is involved - and they flush him out by acting out a version of MR James' 'The Treasure of Abbot Thomas' (as an MRJ fan, I thoroughly enjoyed that and MRJ's cameo!).

Very spooky and atmospheric; good characterisation, and I like the way there's clearly some rivalry with another family (Shakespeare's threaded through very nicely).

The Face Stealer by Sarah Rayne.
This is #3 in the Theatre of Thieves series.
The Fitzglens, a troupe of edwardian gentlemen thieves, are asked to find some stolen Russian artifacts.
The story is a dual timeline- 1909 in London and 1762 during the reign of Tsar Peter III and Tsarina Catherine the Great. Even M R James pops up with the Fitzglens performing a ghost story. It was a great read and so informative about a part of history that I knew nothing about and wanted to learn more.