Even though Killer Kane only rears his evil head for five chapters, his presence looms large over the whole book. He is the cause of all of Max's problems.
Max spends his entire life waiting for his father to return. When he finally does, Max explains:
"I always knew this would happen, that he would come for me, in the night, that I would wake up to find him there." (16.7)
You know what this means, right? That Max has never once in his life felt safe. He has always been waiting for Killer Kane. Imagine spending your life looking over your shoulder. No wonder Max doesn't like leaving the house.
Even though Kenny continues to deny it, we all know that he killed Max's mom. And once he's released on parole, he continues to rack up quite the rap sheet:
They've got Killer Kane where they want him, in violation of parole, in violation of a restraining order, abduction of a minor, and two counts of attempted murder, me and the heroic Biker Babe. (21.5)
Now that they've finally put Killer Kane behind bars, Max's life will probably feel safer. It's a little symbolic if you think about it. Once his dad is confined to prison, Max is finally free of his fear and can come out of hiding.