Brenda Clough 
Earl in the Shadows 

Marian Halcombe Camlet wakes up in a strange bedroom, in a house she does not recognize. She has a new name, and a job, as the companion to the Dowager Countess of Brecon and Stowe, on the vast estate of Cranmorden in Gloucestershire. How did Marian get here, and why? The Earl of Brecon and Stowe has a secret, but Marian has forgotten it. She has to discover the lost memory, and then resolve the secret, before she can return home.