She fell in love with him and refused to give him back to his owner.
She nicknamed him Baldrick because of his very scruffy look! He doesn't have much hair except for a few tufty bits.
But Baldrick's real owner Jessie Delaney said he wasn't lost at all.
She'd asked a friend to dog-sit while she had an operation. But Dewey - or Baldrick - went for walkies on his own and got lost.
Jessie had almost given up hope of finding him until she discovered he had been taken in by Marty after seeing his photo in the local paper.
The case ended up in court because Marty claimed Jessie might not be his true owner and wouldn't look after him properly.