For clarity: Her husband was assumed dead in a train accident 7 years ago, but his body was never buried, so they don't believe he is dead.
The financial records of the estate don't match up, so they are thinking he faked his own death and is supplying other countries with weapons, which could be seen as treason. They are also thinking that the FL may know about it. (I think?)
The guy from the first chapter who ran with the girl WASN'T her husband but a noble or servant.