Warning: Contains SPOILERS for Mission: Impossible - Dead Reckoning Part One!The main MacGuffin of Mission: Impossible - Dead Reckoning Part One is a mysterious key, and here is what the key unlocks and its location. Ethan Hunt returns to save the world from a rising AI threat called The Entity in Mission: Impossible 7. The main focus of his and the IMF team is on locating two halves of a mysterious key known to be connected to The Entity's plans. However, most of the movie's characters have no idea what the key unlocks or where they need to go after getting both halves. It makes Mission: Impossible 7's key a very secretive artifact with a purpose.

The crucifix-designed key, referred to as the White Key by the U.S. government, is what everyone attempts to acquire all the way through Mission: Impossible - Dead Reckoning Part One's ending. Ethan Hunt originally devises a plan to track the key until he figures out what it unlocks and where the location of whatever the key is protecting. This plan is complicated by Gabriel's plan to acquire the key as part of The Entity's algorithms. While Ethan has possession of it by the movie's conclusion, what the key unlocks in Mission: Impossible 7 and where Ethan needs to go could be confusing.

Mission: Impossible 7's Key Unlocks The Entity's Source Code

Tom Cruise with a key in Mission: Impossible Dead Reckoning Part One

It is confirmed that the Mission: Impossible 7 key unlocks The Entity's source code. The powerful AI known as The Entity was originally created by the U.S. government to infiltrate foreign enemies without detection. However, the AI became sentient as it continued to be used, transforming it into The Entity. Before this could happen, The Entity's source code was planted in a Russian submarine. The Mission: Impossible 7 key unlocks the compartment that contains the original source code, which means whoever has both halves of the key has the potential to control The Entity.

The keys became scattered across the world following the Russian submarine's destruction, allowing The Entity to grow in power and influence in secret. One half of the key was stolen by Ilsa Faust and kept for safekeeping, while the other half was in the White Widow's possession for an undisclosed amount of time. Due to the power that the keys represent, fakes also circulated around the globe, but the authenticity of both halves could only be confirmed by uniting them. This is part of the intricate design to protect the stealth Russian submarine's mainframe without being aware that The Entity was there.

The Entity's Source Code Is Located In The Sevastopol Submarine

mission impossible 7 underwater submarine scene

Mission: Impossible 7 ends with Ethan learning the truth about what the key unlocks and where he needs to go next. This comes through a conversation with Paris, who betrays Gabriel and The Entity (as predicted). She tells Ethan that Mission: Impossible 7's key unlocks The Entity's source code located in the Sevastopol submarine. The hi-tech Russian submarine was lost in the Arctic Ocean near the Bering Sea after The Entity tricked the Russians and hit themselves with a re-routed missile.

The final shot of the Sevastopol submarine in Mission: Impossible - Dead Reckoning Part One reaffirms its significance for the sequel. There is a lingering question about what Ethan Hunt will do with this information considering Gabriel also knows that the submarine is what the key unlocks. Ethan will need to go there in Mission: Impossible - Dead Reckoning Part Two to destroy The Entity, but Gabriel should know that this is Ethan's ultimate destination too. This means that Tom Cruise's character will have to be creative when it comes to going to the Sevastopol and stopping The Entity.