Antony Starr as Homelander and Jensen Ackles as Soldier Boy on season five of "The Boys."

Jasper Savage/Prime Video

Warning: Spoilers ahead for season five, episode six of The Boys.

Soldier Boy’s decision to voluntarily give Homelander the key to immortality in the latest episode of The Boys sets up a Herculean uphill battle for the titular vigilantes.

“I think it was almost this passing on of the torch, and it was like, ‘If you want to live like this and you want to deal with it, then be my guest,’” Jensen Ackles, who portrays Soldier Boy, said of the shocking move in season five, episode six. “But I feel like if he wasn’t his son, it probably would’ve been an absolute no-go.”

“I played this sense of, 'I hope you can do it better than I did,’ and giving his son a chance to be able to do that meant having to give him the V1,” he continued. “And then we’ll see in episode seven a little bit more of why he did that.”

In episode six, “Though the Heavens Fall,” The Boys attempt to retrieve the last known vial of V1 from Bombsight (Mason Dye), a member of Soldier Boy’s first team who also survived Dr. Frederick Vought’s first and most potent version of Compound V. To draw out Bombsight, The Boys kidnap Golden Geisha (Naoko Mori), his old flame.

Sister Sage (Susan Heyward), who’s secretly working on her own plan to prevent Homelander (Antony Starr) from getting his hands on V1, calls in Soldier Boy, knowing that he hates Bombsight and won’t resist the opportunity to fight his old teammate. Sage is also confident that no one hates Homelander more than Soldier Boy, and she’s certain because people are predictable.

But even the smartest supe in the world couldn’t predict that Soldier Boy would have a change of heart toward his biological son.

During their confrontation, Bombsight says that Soldier Boy was the epitome of what Vought hoped a supe could be and was favored by Clara Vought/Liberty Bell (Aya Cash), also known by her season two persona, Stormfront.

Soldier Boy then offers to use his powers to remove the V1 from Bombsight’s system so he can enjoy mortality on his own terms, and in exchange, Bombsight gives him the V1 dose. After going through with the deal, Homelander crashes the scene.

Soldier Boy says that Clara used to say he was the ultimate example of a supe’s true potential.

“But she was wrong,” he continues. “She hadn’t met you yet.”

Then, Soldier Boy hands Homelander the V1, much to the shock of Sage and The Boys. The episode ends with Homelander injecting himself with V1, while Billy Butcher (Karl Urban) tells the gang to run.

“He’s kind of come to a point where he feels like, ‘Well, this is the only legacy that I have to leave the world with, and if I’m going to be here and I’m going to be stuck on this planet forever, then it might as well be my son, and we’ll just kind of figure it out together,’” Ackles explained. “I think it’s that paternal softness that he finally finds.”

It’s a decision that might surprise fans. Since his debut in season three, Soldier Boy has never passed up an opportunity to express his disdain for Homelander, calling him everything from pathetic to an “asexual weirdo.”

Ackles pointed to season five, episode four as a turning point in Soldier Boy’s attitude toward Homelander.

In the episode, Soldier Boy betrayed Homelander by locking him in a supe-proof cell with enriched uranium at Fort Harmony, weakening him. When Homelander eventually broke out of the cell and found Soldier Boy, he opted not to take revenge and instead walked away.

Ackles said that Homelander’s lack of retaliation “maybe softened Soldier Boy’s heart a little bit, and he thought, well, maybe there is a future for him and me. And the only way to really get that future would be to give him the V1.”

With V1 now running through Homelander’s bloodstream, the mercurial supe is seemingly unstoppable, leaving The Boys in dire circumstances in the series’ final two episodes.

The first six episodes of season five of The Boys are streaming on Prime Video. New episodes release weekly on Wednesdays, culminating in the series finale on May 20.