“Stop! Help! He’s going over!”

Caitriona Balfe didn’t know it at the time, but the way she uttered those five words during her Outlander audition guaranteed that she’d eventually make the journey through the mystical standing stones. This exclusive sneak peek at the Starz series’ casting process tells the story.

VIDEO Outlander Trailer: Black Jack Is ‘Not Quite Finished’ With Jamie and Claire

The part of Claire, a time-traveling nurse who winds up married to an 18th-century Scot, “is the show, in a lot of ways,” executive producer Ronald D. Moore narrates. And when the Powers That Be heard Balfe utter Claire’s lines, co-executive producer Maril Davis adds, they’d found their Future Mrs. Fraser.

Add in the screen test with Sam Heughan, and it was a done deal. “As soon as they got together, we just knew,” Davis recalls.

The first half of Outlander‘s first season is available on DVD and BluRay on Tuesday. Until then, press PLAY on the video at the top of the post to watch Balfe in action.