Lewis MacDougall plays Conor O'Malley, a young boy who's bullied at school and whose mother is ill with an unspecified disease (although cancer seems likely). A local yew tree pulls up its roots, and comes to tell him stories (voiced by Liam Neeson) over several nights. As his mother gets worse, his American father (Toby Kebbell) shows up, and he has to go live with his grandmother (Sigourney Weaver) - who he doesn't like.
The story is about dealing with fear and grief. The idea of an animated tree playing opposite a kid actor had disaster written all over it - but director J. A. Bayona chose a really good child lead, and - despite heavy use of the CG-animated tree - managed to bring deep pathos rather than unintentional comedy in blending the animation into our reality. The result is a beautiful and heart-breaking story that you won't soon forget.