For marathon bombing survivors Jessica Kensky and Patrick Downes, the road to recovery since the 2013 attacks has been tough. But adjusting to their injuries got a whole lot easier once they met their service dog, aptly named, Rescue.

“I mean he just lightened every dark moment and gave us something happy and exciting to look forward to at a time that was marked by such tremendous loss, of not just our limbs, but our plans, and our future, our apartment, our happiness, our freedom,” Kensky said of Rescue, who sat beside her during an interview Tuesday on Greater Boston.

The black lab is now the star of a new children’s book that Kensky and Downes wrote together called “Rescue & Jessica: A Life-Changing Friendship,” which reimagines Jessica as a young teenager learning to get by with her new prosthetic legs.

In 2013, the then-newlyweds both lost a leg in the explosions and two years later, Kensky’s remaining leg had to be amputated. Kensky said she learned the benefits of having a service dog from NEADS, an organization which helps train them. She later got Rescue, who now helps her stand, fetch things and open doors.

Kensky said writing a book for kids was “a very natural evolution” for the couple and said she often founder herself answering kids’ questions about their prosthetics and about Rescue. “We found ourselves constantly explaining these things at the grocery store, in the elevator, in the parking lot, and we just decided we needed to do it on a bigger scale.”

“They shoot from the hip with curiosity and you just can't help but be charmed by it and want to engage them in the conversation,” Downes added.

Kensky said, after what she and her husband have been through, writing the book was a cathartic experience for her.

“It was fun to get into kids' heads and to get into Rescue’s head, because we see him having these thoughts and this personality, but to get that down on paper was fun,” she said.

To watch Jessica Kensky and Patrick Downes' interview in its entirety, click on the video player above.