Paul McCartney, who lost his wife Linda to breast cancer in 1998, says he's comforted by thoughts that her spirit lives on. "After Linda died, I think all of us in the family would hear noises or see things and think, 'That's Linda, that's mum...' And I think in some ways, it's very comforting to think she's still here," McCartney told ABC's Good Morning America. McCartney said he has been compelled to write poetry since Linda's death, including a poem called "Her Spirit" in which Linda's spirit visits him in the woods, in the form of a white squirrel. "You don't know if it's true. But it's a great thought. And it's an uplifting thought," he said.