Marvel’s The Incredible Hulk movie took it for granted that audiences already knew who Bruce Banner was and how his story usually plays out.

The Incredible Hulk starts with Edward Norton’s Bruce Banner on the run, hiding from General Ross in Rio de Janeiro. However, Banner was not just hiding. Bruce was working on a cure for the Hulk, which is usually the character’s biggest obsession during the initial years following his Gamma radiation accident. Bruce Banner obviously could not use a phone or go to a lab without risking being tracked down and arrested. However, Banner had access to a secure line of communication with a mysterious scientist who presented themselves as Mr. Blue. Banner, for obvious reasons, went by Mr. Green. Together, Mr. Blue and Bruce were close to finding a cure.

Mr Blue Is Marvel Comics Character Samuel Sterns

tim blake nelson as samuel sterns the leader in The Incredible Hulk

After Bruce Banner was found in Brazil and transformed into the Hulk for the first time in almost 200 days, the character decided to return to the United States to meet Mr. Blue in person. The Incredible Hulk reveals that Mr. Blue was Samuel Sterns (Tim Blake Nelson), a Marvel Comics character whose story is deeply tied to that of the Hulk. While Samuel Sterns becomes a Hulk villain in Marvel Comics, the scientist was indeed trying to help Bruce Banner during The Incredible Hulk. That said, Sterns was fascinated with the Hulk's powers and wanted to keep studying Bruce Banner’s blood.

However, despite their best efforts, Banner and Sterns could not cure the Hulk. In fact, “Mr. Blue” ended up helping to create the Abomination instead. Aware that Sterns had been helping Banner and had access to his blood, Emil Blonsky (Tim Roth) ordered Sterns to make him the same as the Hulk. While Blonsky can be very intimidating, Samuel Sterns was happy to help him become a Hulk-like creature. This indicated that The Incredible Hulk’s Mr. Blue was not very trustable after all. Sterns wanted to learn more about the Hulk’s powers and perhaps even how to create more Hulks, regardless of how dangerous it was.

There are a few differences between The Incredible Hulk’s Mr. Blue and Marvel Comics’ Samuel Sterns' backstory, though. In the comics, before the accident that would make him one of the most intelligent people on Earth, Sterns was not a genius. The Incredible Hulk’s Sterns, on the other hand, was an already established scientist smart enough to conduct successful experiments with the Hulk’s powers. In addition, the events that led Samuel Sterns to become a villain in the comics were not tied to the Hulk. In The Incredible Hulk, the accident that seemly made Samuel Sterns into the Leader happened amidst the Hulk crisis in New York.

Samuel Sterns Becomes Hulk Villain The Leader At The End Of The Incredible Hulk

Tim Blake Nelson as The Leader in The Incredible Hulk.

After Blonsky becomes the Abomination in The Incredible Hulk, the creature hits Sterns and destroyed the whole lab. Samuel Sterns’ head got injured, and multiple chemicals got into his body. Sterns’ final shot in The Incredible Hulk sees him with a giant, weird bump on the forehead. This scene was a tease that The Incredible Hulk’s Samuel Sterns would become Hulk villain the Leader. In Marvel Comics, after going through a similar accident that alters the chemistry of his brain and deforms his head, Samuel Sterns takes on the “Leader” alias. With an absurd intellect, the Leader posed himself as a threat to the entire world.

However, The Incredible Hulk’s Leader teaser ed the list of MCU storylines that were abandoned. Distribution rights issues prevented Marvel Studios from making another solo Hulk movie, which is why The Incredible Hulk 2 never happened. In addition, Edward Norton was recast with Mark Ruffalo for The Avengers. For years, it seemed like Banner’s corner of the Marvel Universe would never be revisited in the MCU. This has recently changed with the Abomination returning for two MCU Phase 4 appearances. Likewise, General Ross (recast with Harrison Ford), Betty Ross (Liv Tyler), and Samuel Sterns will all appear in Captain America: Brave New World.

Related: The Incredible Hulk Ending Explained

Samuel Sterns’ return to the MCU more than 15 years after The Incredible Hulk is massive news for the Hulk and for the franchise as a whole. Sterns likely returns in his Leader form, finally paying off The Incredible Hulk’s ending. Pairing Captain America with a Hulk villain may sound surprising, but the Leader can work as an Avengers-level villain whose actions go beyond Bruce Banner. According to Captain America 4’s director Julius Onah, “Sam Wilson has an incredible adversary in The Leader, played by Tim Blake Nelson, this brilliant mastermind who's always 1-2-3-4 steps ahead.”