Michael Douglas is revealing a long-held secret.

More than forty years after he and Kathleen Turner sparked interest with their onscreen chemistry in the 1984 film Romancing the Stone, Douglas—who was separated but still legally married to Diandra Luker at that time—admitted that he and his co-star did engage in an affair after years of denial.

Douglas, who has been married to Catherine Zeta-Jones since 2000, recounts meeting Turner in his new memoir One Helluva Ride, highlighting their immediate mutual attraction.

“The chemistry I had with Kathleen Turner was so strong, audiences have been certain for years that we were in a relationship while making the film,” he writes in the book, which is set to be released on Oct 6, according to an excerpt published by People. “The official story was: Yes, we confessed, we had amazing chemistry. Yes, we were both, as Kathleen said, ‘terrible flirts,’ and yes, we were both tempted, but nothing ever happened between us.

But, as he pointed out, “That was a lie.”

The 82-year-old stated that the couple lied to protect his then-wife Luker, with whom he shares son Cameron Douglas.