Inferno (S01E15)

An explosion at a chemical plant draws in Immortal Talia, prompting Nick to take a job from the factory's owner, Garrett. He claims that a prototype formula for plastics has been stolen. Amanda, an acquaintance of Talia’s, begins to dig deeper and learns that Garrett, Talia's lover, possesses a sample of her blood and intends to replicate her immortality. However, Talia, a former revolutionary who once saved Amanda during the French Revolution, is now motivated by greed and has stolen a viral plague from Garrett to sell to terrorists. As Nick works to disarm a bomb Talia set as a diversion, Amanda confronts Talia. Although she initially spares her, Talia’s relentless pursuit forces Amanda to take her head. The ensuing Quickening eradicates the virus for good.