It's bad to lose someone's pet.
Leah is pet sitting her neighbor Chris's dog, Sparky, and is taking him for a walk when a cat runs past, and he takes off chasing it.
Leah wants to react to Sparky breaking away from her.
"Leah yells at Sparky to ""heel"" and he stops right on his tracks."
Leah panics and lets Sparky get too far away before she begins to look for him, and now it's too late.
Chris is happy that Leigh took great care of Sparky while he was gone.
When Chris returns he is angry because Leah failed to keep Sparky safe.