The Boys showrunner Eric Kripke teases what’s going on inside Billy Butcher’s (Karl Urban) head at the end of the season 4 opener. Prior to the show’s launch, it was revealed that Butcher, the Boys’ leader, was terminally ill as a result of Temp V.

The serum is a modified version of Compound V that grants people temporary superhuman abilities. Butcher surpassed the maximum amount recommended for the new medicine, resulting in brain tumors. However, the episode implies that there may be further Temp V negative effects that he has yet to encounter.

In an interview with Variety, Kripke teased what the ending of The Boys season 4 premiere signifies when something moves inside Butcher’s temple. While the consequences of Temp V are fatal, Kripke believes that scientists do not yet understand all the medicine is doing to the vigilante’s body. Check out Kripke’s remarks below:

We established at the end of Season 3 that the amount of Temp V he was shooting in his veins was going to 𝓀𝒾𝓁𝓁 him. And sure enough, it is. But ultimately, V is a mysterious and insidious drug, and it does really screwed up things to you. And it’s just starting to hint that there’s more going on inside of Butcher than maybe the doctors have found.

Did The Boys’ Spinoff Already Hint at Butcher’s Fate?

The Boys Presents: Diabolical Had A Unique Tumor Storyline

While Kripke confirms some of Temp V’s side-effects have yet to be seen, he doesn’t offer any major hints about what the effect seen in The Boys season 4’s premiere is. The comics don’t offer any insight either, as Temp V is used frequently in the source material without adverse effects. However, The Boys‘ animated spinoff, The Boys Presents: Diabolical, might hold a clue about the vigilante’s diagnosis. Butcher appears to have something living or moving within his temple, which is reminiscent of a character whose tumor mutated from Compound V in the spinoff series.

The Boys Presents: Diabolical features Sun-Hee (Youn Yuh-jung), a pancreatic cancer patient. With barely a few days left to live, her husband grabs Compound V and administers it to her. Compound V impacts her malignant cells, causing her to acquire a sentient tumor, in addition to giving her superpowers.The tumor is a separate creature from her, and it finally separates from her body, continuing to grow and use its tentacles to bring damage until Sun-Hee utilizes her powers to fight it.

Butcher and Sun-Hee differ in terms of tumor kinds and serums used. However, witnessing something tentacle-like moving in Butcher’s temple suggests that he, too, may grow a live tumor. Perhaps he’ll get a superpowered tumor. A sentient tumor would surely coincide with The Boys’ crazy and unsettling inventions, and it may not be as easy to separate from Butcher as it was from Sun-Hee. That’s just one possibility, and it’s unclear what side effects Butcher may face in The Boys season 4.