Harrison Ford transforms into the Red Hulk in ‘Captain America: Brave New World.’ Here’s how and why.

• Harrison Ford plays President Thaddeus ‘Thunderbolt’ Ross in “Captain America: Brave New World.”
• The former military general transforms into the Red Hulk as part of a conspiracy against him.
• Here’s how and why Ford’s character is given a monstrous makeover.

Warning: Spoilers ahead for “Captain America: Brave New World.”

“Captain America: Brave New World” revolves around a conspiracy against President Thaddeus “Thunderbolt” Ross (Harrison Ford) which forces him to transform into the Red Hulk by the end of the film.

It’s the first Marvel movie since Chris Evans left the franchise after “Avengers: Endgame,” and Anthony Mackie took over as Captain America.

In “Brave New World,” Ross is eager to make an impression in the first 100 days as US president. His main drive is to negotiate a treaty with India and Japan to mine the giant dead alien sticking out of the Indian Ocean after 2021’s “Eternals.”

But an unknown villain starts using brainwashed soldiers to attack Ross, before also turning on India and Japan’s respective military presence in the Indian Ocean before they can make the treaty.

All of this raises Ross’ fiery temper until he’s red in the face. Here’s why Ross turns into Red Hulk.

Samuel Sterns, a character from ‘The Incredible Hulk,’ returns to get revenge on President Ross

Samuel Sterns (Tim Blake Nelson) is the mastermind behind the conspiracy against Ross. He first appeared in 2008’s “The Incredible Hulk.” Toward the end of that film, a drop of Bruce Banner’s (Edward Norton) irradiated blood splashes into Sterns’ head wound and causes his brain to expand, making him infinitely smarter.

In “Brave New World,” Sterns explains to Wilson that Ross imprisoned him in an underground military base to force him into making advanced weapons for the United States.

He also found a solution for Ross’ severe heart condition and provided him with cutting-edge medication to keep him alive. In return, Ross promised he would free Sterns when he was elected President, but instead, he left him to rot in prison.

Sterns wants to take revenge by turning him into a monster to destroy Ross’ political career.

Sterns is secretly dosing the President with gamma radiation via his medication, and by the end of the film, there is enough in his body to transform him into the Red Hulk when his temper hits boiling point during a press conference.

The Red Hulk goes on a rampage through Washington, D.C., and destroys part of the White House. But following a lengthy fight with Captain America, Ross regains control and returns to normal.

In the comics, Ross becomes the Red Hulk after his daughter dies

The Red Hulk first debuted in March 2008’s “Hulk #1,” but the monster’s true identity was kept secret for over two years until “Hulk #23” in August 2010.

A flashback in issue #23 explains that Ross’ daughter, Betty, was killed by Abomination, one of the Hulk’s archenemies.

Ross’ grief combined with his hate for the Hulk, pushed him to work with Sterns — who goes by “The Leader” in the comics — and another supervillain, Modok, to gain the Hulk’s powers.

Ross’ body emits heat because the gamma radiation affects him differently than Bruce Banner, which is why he’s red, not green.