Let Him Go: How Kevin Costner Helped Diane Lane 'Feel Emotionally Exposed' During Making of Movie

The two actors costar as husband and wife Montana ranchers in the new thriller Let Him Go, out Aug. 21

Photo: Courtesy Focus Features

There's nothing like the fierce protection of family.

In the new thriller, Let Him Go, Kevin Costner, 65, portrays retired sheriff George Blackledge married to his wife, Margaret, played by Diane Lane, 55. Following the sudden death of their son, the couple leave their Montana ranch to rescue their young grandson from dangerous circumstances involving a family living off the grid in the Dakotas.

When they realize the family has no intention of letting the child go, George and Margaret are left with no choice but to fight to get him back.

Onscreen, Costner and Lane's chemistry was fueled by their mutual respect for one another as actors. "Kevin is both a great team player and an encouraging leader," Lane tells PEOPLE. "He is fully invested in making things as good as possible."

The actor was impressed with Lane's grit and femininity in the role. "She's a great scene partner. She played this stubborn, vulnerable woman without any of the glamor she naturally possesses," he says. "She just makes every guy feel comfortable. There's an art form to that."

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One day on set early in the production, the two were preparing for a scene when Costner, who is also a musician, shared some of his music with Lane.

"Kevin took his headphones off—he’s often listening to music that he creates and performs—and placed them on my ears," she recalls. "It was a song that he was proud of and wanted to share, and he knew it would melt my heart."

The song also made Lane feel "so emotionally exposed in service of the scene we had before us to film that day," she says. "Never forget this man is a masterful director in addition to his other talents! As an introvert, I was grateful to him professionally and touched personally."

The Oscar winner, whose band, Modern West, is releasing a new album, Tales From Yellowstone, tied to the actor's hit Paramount Network western series, is "sincere and from-the-heart, no BS, innately kind, funny and open," Lane adds. "He loves his fans and doesn’t take them for granted, same goes for all crew and cast. He is also a natural raconteur."

Let Him Go is now in theaters.