You can always trust Vin Diesel to tell the absolute truth about his projects, even when the studios want him to keep quiet.

In a recent interview with io9, the 'Guardians of the Galaxy' star admitted he was told about the sequel's emotional plot during a joyous occasion.

"I've heard the story pitched to me from my friend James Gunn over at my house on my son's birthday," Diesel said. "So [I know] as much as you can absorb during a little kid's fifth birthday party. But it's emotional. He's approaching it from the point of character. And I think the audience is really gonna respond to that."

But before he lends his voice to Groot once again, Vin Diesel still needs to promote his new film 'The Last Witch Hunter,' which he admits owes a lot to the author of 'The Lord of the Rings' and 'The Hobbit.'

"I pulled a lot from [J.R.R.] Tolkien on this," Diesel said. "I mean, when you really look at Tolkien, when you really look at his secondary universes, if you distill it down to the one thing that's probably the most important, the thing that he himself as an author was exploring, he was exploring death."

Vin Diesel explained that his take on immortality is influenced chiefly by one of J.R.R. Tolkien's best works.

"'The Silmarillion' was probably one of the first fantasy pieces that played with immortality that wasn't straight up deity mythology. As an author, he's playing with immortality in this really cool way," he said. "Tolkien proposes that mortality is a gift. Immortality isn't a gift, it's the mortality that's the gift. And which is something that we were kind of close to and I was able to kind of factor into our mythology."

'The Last Witch Hunter' hit theaters on October 23 while 'Guardians of the Galaxy Vol. 2' is scheduled for release on May 5, 2017.