Boy meets beast is the basic premise of J.A. Bayona's latest awe-striking drama, A Monster Calls. Bringing heart and life to this boy and beast are co-stars Lewis MacDougall and Liam Neeson, one a child actor who's only previous role was a bit part in Pan, the other one of the most iconic tough guys of the 21st century cinema thanks to thrillers like Batman Begins, The Grey, and the Taken trilogy.

In A Monster Calls, MacDougall stars as poor Conor O'Malley, a young boy whose not only facing down bullies at school and his stern grandmother (Sigourney Weaver) at home, but also the impending death of his terminally ill mother (Felicity Jones). However, when a massive monster (Neeson) in the form of an ent-like yew tree crawls from the ground to his bedroom window, Conor makes an unlikely friend when he needs it most.

Instead of pure animation, director J.A. Bayona favored a motion-capture approach that made Neeson's performance full-bodied and the production tricky. When Screen Rant sat down with Neeson and MacDougal we asked about this fascinating process, and how Spider-Man: Homecoming's Tom Holland manages to swing into it--much to Neeson's (mock) chagrin!

Can you guys tell me a little bit about how you guys actually shot these scenes? Because I know you did motion capture.

Liam Neeson: Yes. I did motion capture with Lewis. He was there. We shot in this special little "mo-cap", as it's called, studio outside of London for the first two weeks before principal photography started. It was Lewis, myself, our director J.A. Bayona, in this space with these wonderful computer guys and we acted our scenes and were directed very, very closely by Mr. Bayona and the computer guys added all this digital makeup to me, to the monster. I was acting to a doll this size on a house this size to get the perspective right. For the most part, Lewis was off-camera giving me this extraordinary acting performance.

That's a really intense way to basically start the lead. This is a huge role where you're in every scene and then to start like, "We're just going to put you off to the side and deliver all your lines." What was that like for you?

Lewis MacDougall: It was different but extremely beneficial for me to have the opportunity to rehearse because Liam wasn't actually on set when we were shooting the film. But it was great for me to actually perform with him and actually do the scenes with a real person there and be able to take that onto the set.

I also heard that Tom Holland came by one day just to visit and ended up doing some mo-cap too. Did you get to work with him?

Lewis MacDougall: He didn't do mo-cap, he basically, Tom did make a couple of set visits - as you know he knows the director very well from The Impossible - and one day we needed somebody just to read the monster's lines. It would occasionally be a recording of Liam but no matter how fantastic the actor is, if it's a recording it's hard to act with that. So you get a real person there, so Tom did stand in for the monster one day.

That's pretty cool. So you got to act with Spider-Man?

Lewis MacDougall: Yeah. *laughs*

Liam Neeson: I don't think that's cool...I'm hearing this for the first time. Spider-Man dared to play the monster? *laughs*

This is actually your third voiceover role, between The Chronicles of Narnia and The LEGO Movie...

Liam Neeson: I'm gonna stop you. It's not a voice-over.

Yeah, that's incorrect.

Liam Neeson: It's motion capture.

Oh no, right. Because it is motion capture.

Liam Neeson: It's motion capture. Yeah.

So is it your first motion capture?

Liam Neeson: First motion capture, yeah, yeah. Very interesting process and very difficult for the first day because you're in an onesie with ping pong balls attached to you. But the process itself, it didn't interfere with our acting and interaction with J.A. Bayona, which was very intense and very intimate. And then these computer guys, I had all this digital makeup too. It's extraordinary. So it's not a voice.

That's my mistake.

Liam Neesan: Andy Serkis went to pains to put that across from Lord of the Rings years ago, because it wasn't a voice that was him playing Gollum. Incredibly.

So how do you take on the physicality of a walking yew tree? There's not like there's a lot of reference or research for that.

Liam Neeson: It's an act of the imagination, isn't it? Patrick's book, he's written a classic fairy tale...actually, it's not a fairy tale, it's a parable. So I took it from that, from the book and used my own imagination and hung out with a forest of yew trees for three weeks before we started shooting that helped. Laying with them...naked.

The key thing of this is sympathy for the monster. What do you think is relevant in that theme right now?

Liam Neeson: Ask me that again? I'm sorry. I didn't quite understand. No no, go on, ask it again.

Is the idea of sympathy for monsters, what of that theme do you think might be relevant?

Liam Neeson: Well, I don't think he is a monster. Conor's characters, Conor has conjured this figure up from a yew tree at the back of his house, from his grandfather, from his mother's drawings and stuff. It's an amalgamation of something he's conjured to be his buddy. To us it looks like a monster but in actual fact it's a healing spirit. Because he has nobody to talk to in the movie, this character.