Toronto-based illustrator Kathryn Durst says she's found a true collaborator in Paul McCartney after working closely with the rock legend to bring his bedtime tale for grandchildren to the page.

McCartney revealed the cover of his upcoming children's book "Hey Grandude!" featuring Durst's drawings on social media Wednesday.

"I’m excited to share the cover of my new children’s book Hey Grandude! which will be out later this year. I’ve worked on this with a great illustrator called <a href="https://twitter.com/KathrynDurst?ref_src=twsrc%5Etfw">@KathrynDurst</a> and I hope you enjoy it as much as I do!" 😃 Pre-order your copy HERE: <a href="https://t.co/wl2jyIZ16N">https://t.co/wl2jyIZ16N</a> <a href="https://t.co/U3RThIntGH">pic.twitter.com/U3RThIntGH</a> —@PaulMcCartney

Durst says some authors take a hands-off approach to the visual side of storytelling, but she and McCartney spoke several times on the phone to discuss his ideas for the illustrations.

She says McCartney had direct input into the "retired hippie-ish" design of the titular Grandude, inspired by a nickname by from one of his eight grandchildren.

When she met McCartney in Montreal last fall, Durst says she felt like she was seeing an "old friend."

"Hey Grandude!" is set to be published by Random House in September.