H. G. Wells 
Love and Mr. Lewisham 

Young, impoverished and ambitious, science student Mr Lewisham is locked in a struggle to further himself through academic achievement. But when his former sweetheart, Ethel Henderson, re-enters his life his strictly regimented existence is thrown into chaos by the resurgence of old passion. Driven by overwhelming desire, he pursues Ethel passionately, only to find that while she returns his love she also hides a dark secret. For she is involved in a plot of trickery that goes against his firmest beliefs, working as an assistant to her stepfather — a cynical charlatan ‘mystic’ who earns his living by deluding the weak-willed with sly trickery. (Goodreads)