William Shatner is still saddened over the distance that came between him and "Star Trek" legend Leonard Nimoy — and, to make matters worse, he doesn't know why their relationship turned icy to begin with.
In his new book, "Live Long and… What I Might Have Learned Along the Way," William dishes on the pain he still feels.
"Until the day I die, I will still wonder what caused that rift," he writes. "After all the years we had spent together, after the bond we had forged, what could I have done that was so irreparable that he couldn't even talk to me about it?"
The two were once considered best friends, but their estrangement eventually got so bad that William didn't even attend Leonard's funeral in 2015 because he felt unwelcome. Instead, he attended a charity function.
"I feel really awful. Here I am doing charity work and one of my dearest friends is being buried," he tweeted at the time.
Afterward, William showed a soft spot for his old friend, gushing about him on Twitter.
"What's the best thing he's ever said to you?" one person asked about Leonard. William replied, "I love you."
Asked what he learned from the beloved Spock, William said, "I learned to be more serious I think he learned to be less."
Eventually, he was asked if he had any regrets with regard to his relationship with Leonard, which prompted William to respond, "That it couldn't have lasted a lot longer."