A psychotic alien cab driver, is inexplicably attacking innocent humans and draining them of their vital "life force". While attempting to overtake the disturbed cabbie, Kay is attacked and imbued with the alien's "essence". Psychically bonded to the alien and capable of feeling his pain, Kay refuses an antidote reasoning that his condition will aid in capturing the rogue Alcidian. As the pursuit escalates, Kay identifies more closely with the deranged alien and eventually turns against his fellow agents. It's a life or death situation for their partner; Jay and Elle must quickly devise a plan to bring down the violent Alcidian without harming Kay.