What family revelation does Len share with Abigail? What is Len's purpose in sharing it ?

Abigail asks Len how his wife died. He tells her she committed suicide. She asks why his wife killed herself and Len tells her he doesn’t know but that the question preoccupies him when he is not thinking about Susie’s murder. Abigail smiles when he says “your daughter’s murder” because no one in the neighborhood ever talks about it directly. She has him repeat the phrase, and then she kisses him. This revelation puts them on a more personal level. Susie isn't just a case to solve.