William Ennis was an employee at the Sierra Madre. His locker can be found at the Puesta del Sol switching station, unlocked by a key found near Christine Royce's position for the gala event. He is referred to as "old man Ennis" in a terminal entry in the same location. His locker contains a note titled toxic samples which suggests that Ennis was one of the workers in the hazard suits to protect the Sierra Madre against the Cloud.