Paging Dr. Ford! Newly engaged Oscar nominee Harrison Ford is back in front of cameras in an all-new emotional drama starring opposite Brendan Fraser and Keri Russell, and ET was the only show invited to the Portland, Oregon set to see the stars in action!

But first, our Mark Steines is one of the first to offer his congratulations to the 'Indiana Jones' star on his engagement to longtime girlfriend Calista Flockhart.

"Thank you very much," says Harrison, confirming their happiness by joking, "You'd be the first to know if we weren't, wouldn't you? Yes, of course we are. I'm delighted."

In this groundbreaking CBS Films production -- currently untitled and due in theaters in April 2010 -- Harrison plays a scientist in a heart-wrenching story inspired by real events about a couple, John and Aileen Crowley (Brendan and Keri), whose children are dying from a rare genetic disorder -- and it's up to Harrison's character to save the girl and boy.

"This is an extraordinary story of a guy who went against all odds," says Harrison. "I thought it was a sort of opportunity to tell an uplifting kind of story about very courageous people."

"What parent wouldn't do anything for their kids?" asks Brendan. "This is the crowning example of an individual who just would not take no for an answer. He was not a scientist by any means, but he found one who was a bit of a renegade for sure -- but brilliant.

"This isn't going to be a sad story," adds Keri. "This is a story about people who are surviving this, and these are really extraordinary people."

"The personal part of the Crowleys is an important part of the story," says Harrison of the film's real-life inspiration. "He's a remarkable guy, he's a remarkable intellect, he's a compassionate, wise fella -- and fun at a party."

Watch ET for more with Harrison, Brendan and Keri from the set!