Grim is an adult Baryonyx that was originally intended as an exhibit for the Jurassic World theme park on Isla Nublar. Grim was part of a trio with two other adult Baryonyx specimens, Chaos and Limbo. Each Baryonyx was easily identifiable via a distinctive color scheme, and Grim was easily identifiable through its Light greenish coloration, and tinted red spots around its eyes.
Prior to the Jurassic World Incident, Grim was among a variety of dinosaurs being held at the Veterinary Clinic station for observation and medical treatment. However, due to the evacuation of the Island, the animals were left in cages and were not freed until Darius and Sammy come across them and take pity on their situation.
The children come across Grim stuck in the cage, and are initially reluctant over whether to free it or not. However, as Chaos and Limbo arrive, they cause the children to scatter, although Darius eventually frees Grim after some indecision, as he witnesses Chaos attempting to free her pack mate.. Reunited, the Baryonyx trio manage to scare away and cause some Stegosaurs to stampede, causing the children to flee the area as well. Grim would later encounter Brooklyn, Yasmina and Sammy as they fled from Chaos and Limbo, taking them by surprise. However, instead of attacking, the animal chose to respond to the distress calls of its packmates, leaving the children alone.
An unspecified amount of time later, the Baryonyx trio would be roaming around the garage at the same time that Bumpy, Hap, Brooklyn, Ben, and Kenji were in the area. Upon seeing Brooklynn open the door to the garage, the Baryonyx trio charged the entrance attempting to attack the kids, however, the garage exploded, stunning them and allowing them to gain some distance from the predator trio.
The humans continued to be pursued by the trio, and they were chased through a host of obstacles, including a cluster of narrow rocks. Seeing that they are outnumbered, Hap begged them to untie him, and he is untied by Kenji as he uses the shock stick against the Baryonyx. To buy time, Hap stayed behind to distract Grim, Chaos and Limbo, as they surrounded him.
The Baryonyx trio would stalk Mitch and Tiff as they left Main Street. Grim saw an opening to attack as they argued, and charged the pair. However, Tiff manages to push Mitch away and shot Grim, dead. The poaches abandon the dead Baryonyx, declaring their intention to return for it after the watering hole. As they depart, Chaos and Limbo approached their fallen comrade, lingering briefly over the body, before starting to track Mitch and Tiff’s last known path.