In The Creature from Beyond, he was attacked by the Lucubra and turned into a mind-controlled slave. He was seemingly cured when Gwen sent the Lucubra back to its home dimension, but his eyes were later seen glowing the characteristic turquoise of one of the Lucubra's slaves, showing that he is still under its control.
In A Knight to Remember, Winston is an Esoterica because he had been mind controlled by the Diagon. Under its control he informed the rest of the Flame Keepers' Circle of where to find Diagon's heart and Ascalon. When Vilgax gained the sword and the heart, Winston, still under the control of Diagon, tricked Vilgax into breaking open the Seal into Diagon's dimension and reuniting him with his heart. When he is taken to the Forever Knights by Ben, Gwen and Kevin, he is nearly beheaded before being saved by Ben.
Ben 10: Ultimate Alien
- Winston is revealed to be the squire of many knights: