The Obsidian Mirror. Book 1

TIME TRAVEL MEETS SCARY FAIRIES - but there's so much more to Catherine Fisher's brilliant Shakespeare Quartet which begins with The Obsidian Mirror ... Jake's father disappears while working on mysterious experiments with the obsessive, reclusive Oberon Venn. Jake is convinced Venn has murdered him. But the truth he finds at the snow-bound Wintercombe Abbey is far stranger ... The experiments concerned a black mirror, which is a portal to both the past and the future.
Venn is not alone in wanting to use its powers. Strangers begin gathering in and around Venn's estate: Sarah - a runaway, who appears out of nowhere and is clearly not what she says, Maskelyne - who claims the mirror was stolen from him in some past century. There are others, a product of the mirror's power to twist time. And a tribe of elemental beings surround this isolated estate, fey, cold, untrustworthy, and filled with hate for humans.
But of them all, Jake is hell-bent on using the mirror to get to the truth. Whatever the cost, he must learn what really happened to his father.