How does guck help widow Douglas? Why does he want his actions to be a secret

Huck overhears Injun Joe explaining how he's going to get his revenge on Widow Douglas's dead husband, who apparently ordered that Joe be flogged, by breaking into the Widow's house assaulting her. Huck is able to save the widow by finding help from the Mr. Jones.

oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooof