How effective is the ending of "Mister Tom"?

The ending of "Mister Tom" was very strange and surprising, especially when Zack died. I really didn't think anything as extreme would happen in the story. Everything was going along nicely in the story when under strange circumstances Zack had to go to London. It was very strange that Zack was the one who was chosen by the author to die. I think it was to symbolise how strong Willie's emotions had become.
Mister Tom must have really have loved Willie to risk going to jail when kidnapping [or rescuing] him. Mister Tom thought back to when Rachel was alive. He thought of what she would do…