Molly Briggs appears in The Beaver in the Otter. She accidentally killed Jimmy "Beaver" Bouvier when he attempted to force himself on her. While the two were working on their college float alone, Beaver approached her and propositioned her for sex. Beaver was always hitting on her, but Molly didn't like him romantically though many thought they were together. Beaver kissed her against her will and to stop him, she pulled the trigger on a nail gun she was holding, shooting him through the aorta by accident.
After Beaver fell off the float, he demanded Molly pull the nail out for him, but she refused as she knew from TV that you don't pull out a nail after being shot with one. Beaver pulled out the nail himself and as it had pierced his aorta, he died as Molly predicted. Frightened that everyone would believe she murdered Beaver as they believed they were together, she put Beaver's body in the school mascot uniform.
After an investigation, Arastoo Vaziri found the nail and Booth and Bones recognized the design on it as being from the float. Booth used the nail gun on the float and gave the nail he fired to Bones for comparison as Doctor Lance Sweets observed those standing nearby. Seeing Molly's nervousness, Sweets identified her as the killer. She later explained what happened to a sympathetic Bones and Booth and was likely let go for Beaver's death, since it was an accident and she was defending herself from a possible rape when she shot him, however she still might suffer charges for hiding the corpse.