Tom Cruise and Cameron Diaz reignite their chemistry on the big screen for the first time since 2001's 'Vanilla Sky,' and only our own Mary Hart is with them on the top-secret Boston set of their new action-comedy, 'Knight & Day,' where they've been doing a lot of their own daring stunts!

"She's done a 180 in a car -- '65 GTO the other night," says Tom. "She does it. She's a very good athlete. Very coordinated and excellent."

A globetrotting adventure featuring big action, big laughs and big stars, 'Knight & Day' finds Tom and Cameron as a fugitive couple on the run - creating an opportunity for plenty of explosive moments along the way, including a sequence in which Tom is hanging on top of a speeding car that Cameron's driving!

"When Tom was on top of the car, and I'm inside the car going, 'Ahhh! Ahhh!,' and he's on the hood of the car flying through the air, you know, cabled to a car, jumping 20 feet across -- I'm like, 'I want an action scene, you guys! I wanna fight! I wanna be on the hood of a car! Write it! Just write it in somewhere,'" exclaims Cameron.

Cameron says not to worry about Tom, however. "He is a professional stuntman," she says. "If he wasn't Tom Cruise the movie star, he would be the best stuntman in the business. He's phenomenal. What he does is, like, crazy."

After letting loose in last year's 'Tropic Thunder,' Tom also shows off more of his comedic chops in 'Knight & Day,' and Cameron reports, "He's hilarious. He's so funny!"

As for the overall feel of the film, she clarifies, "It's not like a wacky comedy; the situations are kind of absurd."

"It's a fun character comedy; adventure, romance -- I don't want to give away too much," adds Tom. "Girl meets boy, boy sees girl, girl sees boy, adventure ensues."

The highly anticipated 'Knight & Day' hits theaters next July 2, 2010.

Watch ET tonight for more with Tom and Cameron!