Martha Rooney (Katie Boland) is an eighteen-year-old autistic girl who lives with her mother Josephina (Amanda Tapping). When Josephina is shot in front of her by fugitive murderers Jake (Scott Heindl) and Penny (Melanie Papalia), Martha is left in the custody of her cousin Nicky (Brooke Burns). Martha remembers everything that happened that evening, but is unwilling to talk about it, and Nicky works with Detective Velez (Nicholas Lea) to find out what she knows. Meanwhile, Jake and Penny are plotting to kill Martha before she talks.
Dancing Trees contains examples of:
- Air Guitar: A variation. During a recital, Martha plays the first few bars of a Fryderyk Chopin piece on a piano, then plays the rest of the song on an air piano, producing orchestral music only she can hear.
- Broken Treasure: During a meltdown, Martha breaks a vase belonging to Nicky. Nicky is upset because her grandmother gave it to her. She tries to fix it, but can't figure out how to get the pieces to fit back together, and considers just throwing it out. But then Martha glues it together for her, and does such a good job that it looks like it was never broken.
- Cry into Chest: Martha cries into Nicky's chest after one of her nightmares.
- Disappeared Dad: Martha hasn't seen her father Mark Heller (Michael Ryan) since her parents divorced, apparently when she was a young child. He now lives in a McMansion with his second wife Joan (Brittaney Bennett) and his three kids who don't know Martha exists. When Nicky drops Martha off with Mark, saying he's the best person available to take care of her, Mark tries to talk her out of it; after Nicky leaves, he promptly dumps Martha in an institution. Nicky ends up getting custody of Martha.
- Flashback Effects: After Nicky leaves Martha with Mark, she has sepia-toned flashbacks of earlier scenes with Josephina and Martha, and especially of her promise to take care of Martha.
- Flashback Nightmare: Martha has nightmares of Josephina's murder and wakes up crying and muttering. While she's half-asleep, she utters one of her first useful clues, "MS-13," referring to the tattoo on Jake's neck.
- Flatline: In the hospital, Josephina makes Nicky promise to take care of Martha. Then she loses consciousness and flatlines a few seconds later.
- I Want My Mommy!: Martha cries for Josephina several times. She doesn't seem to understand that Josephina is dead, because she talks about how cold and lonely it must be in the grave and how she didn't want to go there.
- My Parents Are Dead: While chatting with one of Nicky's customers about mystery novels, Martha abruptly says, "My mom was murdered," to the customer's shock. Then she resumes talking about Patricia Cornwell.
- Picky Eater: Martha won't eat unless her food is arranged in just the right way, with nothing touching.
- Please Wake Up: After Josephina is shot, Martha runs out of the car and starts tapping her arm, saying, "Mom, get up. Ice cream. Ice cream, one scoop. Just one scoop." A variation in that Josephina isn't quite dead, although she will be soon.
- P.O.V. Cam: In shots from Martha's perspective, everything looks shinier and more colorful, and there are floating lights, sometimes colored.
- Security Blanket: Martha spends the first part of the movie carrying a doll around. She throws it after the coffin into Josephina's grave.
- Sensory Overload: Martha follows a customer she's talking to out of the bookstore and down the street. At an intersection, she freezes, overwhelmed by the changing lights and rapidly moving cars. Jake and Penny try to take advantage of her confusion to abduct her, but Nicky runs out to bring her back at the last minute.
- Slow Clap: After Martha's recital, the audience sits in confused silence. Then Josephina starts clapping, and everyone else joins in.
- Super-Speed Reading: Martha has read over 8,000 of the books in the bookstore where Nicky works thanks to this trope. She can read a page in just a few seconds.
- Title Drop: Martha refers to her room at Nicky's house as the dancing trees room because she likes watching the shadows of trees on the ceiling.
- Too Unhappy to Be Hungry: At the institution, Martha is so miserable that she stops eating or talking.
- Troubled Fetal Position: Martha responds to extreme stress by hiding in a closet or cabinet with her knees to her chest, usually with a blanket draped over her head.
