The action film sees IMF agent Hunt face one of his most dangerous enemies yet, a rogue AI programme named The Entity that is capable of altering the truth as we know it and accessing the databases of very world power to alter it to its whim.
His mission is to find the two interlocking keys that open... something, so he brings together his best crew members to get the keys and stop it from getting into the wrong hands.
As it is a two-parter, viewers are no doubt wondering exactly how the film sets up its sequel, which is set for release in 2024.
Here is everything that you need to know, but consider this your spoiler warning.
How does Mission: Impossible - Dead Reckoning Part One set up Part Two?
In Part One, Hunt and the team are racing to figure out a way to get the key they need to have access to The Entity and stop it before it's too late.
After an epic battle on the Orient Express, which is complete with death-defying stunts and a memorable use of the franchise's signature face masks, Ethan manages to fend off villain Gabriel (Esai Morales) and get away with both of sets of keys.
Although Gabriel thought he'd managed to successfully take them, it turns out Ethan pickpocketed the keys from him and he leaves the train in order to rendez-vous with Benji Dunn (Simon Pegg).
The ending suggests the pair will now go on to search for the Russian submarine that was sunk in the arctic at the beginning of the film, as it will prove to be the clue they need to find out what the key opens to hopefully find a way to destroy The Entity.
Gabriel will likely also try and get to the sunken vessel at the same time, meaning Ethan will have to face his old enemy again.
The origins of their feud is hinted at in the first film and it will no doubt be explained in more detail in the second, but what we do know is that Gabriel is the reason that Ethan joined the IMF in the first place.
As things stand, Ethan and his team still don't know exactly what the interlocking key opens so the sequel will likely see them discover what it does and how it connects to The Entity.
Elsewhere, following her experiences with Ethan, Hayley Atwell's Grace meets with Eugene Kittridge (Henry Czerny) and says that she accepts "the choice" to join the IMF, meaning she will embark on her new line of work in the second film and help them out in the next part of their adventure.
IMF tech genius Luther Stickell (Ving Rhames) also decided to go underground in Part One in order to find a way to stop The Entity without it being able to detect him, focusing on analogue rather than digital technology to do so. The agent will hopefully return in a big way in Dead Reckoning Part Two, and his efforts won't be in vain as his mission is certainly one of the most important to the future of humanity.
With the team scattered, the next film in the franchise will likely see them regroup and prepare themselves for the next stage of their battle against Gabriel and The Entity, with them fighting to save the world from the terrifying AI.
Mission: Impossible Dead Reckoning Part One is out in UK cinemas and IMAX now.
Watch: How the Mission: Impossible - Dead Reckoning Part One train stunt was done