Justin Richards seems to be on form these days; this is another tie-in e-book, intended as a prequel to The Snowmen (though as far as I could tell it was not available outside UKania until after the broadcast), a tale of Madame Vastra, Jenny and Strax battling a smoke monster with the assistance of a small boy as viewpoint character. It is a pastiche of Victorian children’s stories with a nod to Leon Garfield (though his Devil-in-the-Fog was set a hundred years earlier), spooky and enjoyable. When we first met Vastra and Jenny, fandom cried out en masse for spinoff stories about them, and I think this and James Goss’s piece for last year’s Brilliant Book shows that fandom was right.