May I borrow your dog?

May I borrow your dog for a few days?
It's for my mother-in-law," explained the mourner at the funeral procession. Tightening the leash, he gestured down at the dog and said, "My Doberman here killed her."

"Gee...That's terrible," commiserated the spectator. "But... Hmmmm... Is there anyway you might lend me your dog for a day or so?"

The bereaved son-in-law pointed his thumb over his shoulder and answered, "Get in line."