At just a few months old, Kalli arrived in her forever home-determined to train her new owners, Laura and Marc Abbott, to be perfect humans.

Brilliant, fearless, and displaying little patience for the antics of other dogs, she was always a spaniel with a mind of her own. Even in the face of obedience classes, the calculating canine was constantly plotting her next move, working the system in any way she possibly could.

But it wasn't just Laura and Marc's lives that Kalli changed forever. As a certified therapy dog, she helped teenage girls with substance abuse problems-and...