The Invisible Man (2000) : 1x23

Presumably the audience voted yes to Hobbes' decision to join Fawkes. Darien, in end-stage Quicksilver Madness, is now obsessed with finding Arnaud. Hobbes sticks close by trying to keep him from killing random bystanders. They catch up to Arnaud, but Hobbes helps him escape when it appears that the maddened Darien will kill him. Darien abandons Hobbes, who is then approached by Arnaud. Arnaud has a malfunctioning Quicksilver gland of his own, and needs to use Darien's as a baseline to get his own fixed. In return, he'll give Hobbes Stage Five Counteragent to reverse Darien's advanced condition. Hobbes helps capture Darien, and a surgeon, Dr. Reynolds, manages to adjust Arnaud's gland. Darien gets the Counteragent, but before it can take effect he tries to kill Arnaud. Arnaud escapes during the distraction when the counteragent kicks in. Later, Arnaud goes to visit Reynolds when he realizes that the surgery did not go quite right, and he is permanently invisible.