Some of the first things the reader hears about Max's father come from the character of Grim. Grim, of course, is the nickname Max gives to his grandfather who has taken him in. Grim's opinions about Max's father all revolve around fear of Killer Kane as a dangerous criminal.
First, Grim says that Max's father's name is “too scary to say.” As the plot moves on to the rising action, the reader learns that Max's Father (Killer Kane) is being released from prison. As a result, Grim reacts further. Grim wants to obtain a gun, but Gram is against it. Finally, Grim's opinion of Killer Kane is confirmed when Grim obtains a restraining order against Kane.
If [Killer Kane] does try to come here, they’ll send him back to prison. ... Everything is going to be okay.
Although this statement is designed to make Max feel safe, Grim still insists that Max stay inside for days. Of course, Grim's opinions are confirmed when Max's dad shows up and ties Max to a boiler.