Cassie Claiborne has problems beyond her control: her pool-shooting father has another wife; her stoic, long-suffering mother is incapable of moving herself mentally away from the kitchen window; and her sister Belle is a tempest of fragility and brilliance.

Third-grader Kaline Klattermaster's father has gone somewhere and his mother cannot seem to keep everything straight now. But the two brothers and one hundred dogs that live in his imaginary tree house -- and his strange neighbor Mr. Osiris Putnaminski -- help him cope with his father's absence, his mother's forgetfulness, and the bullies that torment him in school.