McGinnis was a high-ranking federal marshal of the Union of Allied Planets stationed in or near Saint Lucy's hospital on Ariel. Agent McGinnis was tipped off by Serenity crew member Jayne Cobb, who wished to turn in Simon Tam and River Tam in return for the large reward. Jayne planned to betray the pair during one of the crew's most lucrative jobs, the infiltration of Saint Lucy's hospital. Jayne contacted McGinnis at the hospital; the agent assured him of the reward, and Jayne assured him that the "fugitives" were present. Although Jayne had second thoughts and attempted to escape with the siblings, McGinnis and his team of marshals arrived and apprehended them. McGinnis then made it clear that he was arresting Jayne as well, in order to keep the reward for himself. When Jayne charged McG