Marcus is Ellie's husband, recovering from a bicycle hit-and-run accident. He and his wife recently moved to a coastal house after their daughter left for college. Unaware of David's dangerous nature, he initially interacts with him socially. Later, he is captured and tied up by David at their home. He eventually fights alongside Ellie to defend their family, ultimately intervening to stop David when the antagonist threatens Ellie with a firearm.