It's one of Hollywood's darkest mysteries...Natalie Wood's drowning death.

Wood was one of the most luminous stars in Hollywood, famous for her roles in Rebel Without A Cause and West Side Story.

Questions still linger about what happened that night back in 1981 aboard the yacht called The Splendour.

But now a new book, Goodbye Natalie, Goodbye Splendour, promises to shed new light on the death of one of the most beautiful movie stars of all time.  And its revelations are devastating for Natalie Wood's sister Lana.

"It makes me angry. It makes me incredibly sad," says Lana Wood.

It's written by Dennis Davern, who was actually the captain of The Splendour, the yacht owned by Natalie and her husband Robert Wagner.

"There was a whole lot of jealousy, tension building up as soon as we left the dock."

The subject of that jealousy was Wood's co-star in the movie Brainstorm, a hot young actor named Christopher Walken, who was joining the Hollywood super-couple for a weekend getaway to Catalina Island.
 
Davern says Wagner was jealous that Wood had invited Walken aboard.

"Did he think they were having an affair?" asks INSIDE EDITION's Les Trent.

"I believe so," says Davern.

He says on Wood's last night alive, she and Wagner got into an argument in their stateroom.  "I heard a lot of noises, a lot of yelling.  I knocked on the door of their state room to see if there was anything I could do, and Robert Wagner told me just to go away."

A short time later, Natalie Wood went overboard.  For years, Wagner remained silent about what happened, but last year he published his own memoir about what happened that horrible night.

"We had a dinghy that was tied up next to the boat.  It was banging up against the hull of the boat.  What we think is that she went outside and slipped on the swim step and hit her head and was knocked unconscious and fell into the water."

But now the boat captain is revealing what happened just after Natalie disappeared.  "I said to Robert Wagner, I said, 'Well, let's turn on the searchlight immediately and see if we can see her.'  He says, 'No, we're not going to do that.' "

"He said no?"

"He said no," says Davern.

Wood's body was found floating just offshore the next morning.

Lana Wood, who was a star in her own right, best known for her role as a Bond girl in Diamonds Are Forever, says she believes the captain's account of her beloved sister's final hours is the truth.

"I've known Dennis for a very long time, decades, and I've never known him to be a liar," she says.

But even though the mystery of Natalie's final moments remains unsolved, her sister doesn't blame anyone.

"The bottom line is she's gone and no one can ever fix that."

Robert Wagner's representative said "No comment" when INSIDE EDITION asked about the book.