how did Laura's first husband die? why did he get to that place and what was he looking for there? give examples from the story

On a visit to the Opera with Pesca, he learns that Fosco has betrayed an Italian nationalist society, of which Pesca is a high-ranking member. When Fosco prepares to flee the country, Walter forces a written confession from him in exchange for safe-passage from England. Laura's identity is legally restored, and the inscription on her gravestone replaced by that of Anne Catherick. Fosco escapes, only to be killed by another agent of the society. To ensure the legitimacy of his efforts on her part, Walter and Laura have married earlier; on the death of Frederick Fairlie, their son inherits Limmeridge.