While _Turtles All the Way Down_ deals with serious issues like grief and the toll of mental illness, Hannah Marks imbues the movie with such color and humor that the highs and lows feel even more powerful. _Turtles All the Way Down_ tells a moving story about a teenager's isolating struggle with mental illness, and her resolve to build a life for herself despite it. The entire cast of _Turtles All the Way Down_ brings something distinct and wonderful to the movie. However, Isabela Merced's performance as Aza will likely go down in the books as one of the most impressive of her career. The chemistry between Merced and Cree as Aza and Daisy is perhaps the film's greatest strength — and certainly its greatest love story. Their effortless comedy and obvious care for one another make the friendship feel totally believable, and it makes their fights all the more devastating.