Who is Count Fosco from The Woman in White and what is their importance?

Count Fosco is described as a corpulent, charming, musically-talented Italian. In his sixties, he is married to the forty-three-year-old Countess Eleanor Fairlie Fosco. The couple have no children.

Fosco is a spy in a secret society, and he has betrayed his brotherhood in Italy. He rescued Sir Percival from robbery in Italy, and the two became friends. Fosco owns a cockatoo, canaries and white mice on which he dotes, and he adores Marian Halcombe because she is a formidable enemy. Fosco is also involved in Sir Percival's plan to steal Laura's identity and fortune. By the end of the novel, his body is found in the Seine and buried in Paris.