Full story
Years ago, Wade Wilson used a time machine to try to join the Avengers, but Happy Hogan turned him away. Six years later, Wade has retired Deadpool, broken up with Vanessa and sells used cars. On his birthday, the TVA picks him up. There, Agent Paradox explains that Wade's universe is slowly dying because it lost its anchor being: Logan, Wolverine, who is dead. Paradox wants to speed up the end with a machine called the Time Ripper and offers Wade a place on the Sacred Timeline, without his friends.
Wade steals a TemPad and first tries something desperate: digging up his world's Logan. It doesn't work. So he searches the multiverse for a Wolverine who could take the original's place. He finds plenty, and they all turn him down or don't fit. In the end, he comes back with a drunk, bitter Logan who can't stop blaming himself. Paradox laughs: this one is considered the worst Wolverine of all, the one who failed the X-Men of his world, and he can't serve as an anchor.
To get rid of them, Paradox dumps both into the Void, a wasteland at the end of time where the TVA sends what it doesn't want. There they fight each other viciously until they're captured by the goons of Cassandra Nova, Professor Xavier's twin sister, who rules the place with terrifying mental powers. The two escape and find a resistance of forgotten heroes: Laura, X-23, Elektra, Blade and Gambit. Little by little, Wade and Logan learn to work together, and Logan starts to open up about what went wrong in his world.
Wade proposes an alliance, and the group takes on Cassandra using Juggernaut's helmet to block her powers. Pyro, who was working for Paradox, betrays Cassandra and nearly kills her. Logan convinces Wade to take the helmet off her so they can get home, but Cassandra seizes the chance, escapes with a sorcerer's sling ring and invades Wade's universe. She takes over the Time Ripper and plans to destroy every reality.
Wade and Logan go after her, and Wade's friend Peter shows up to help. Cassandra summons an army of Deadpool variants, and the fight turns into chaos. To stop the Time Ripper, someone has to sacrifice himself. Wade and Logan climb into the machine together and share the energy load, which destroys the Time Ripper and kills Cassandra. Both survive. Hunter B-15 arrests Paradox and confirms that Wade's universe will be fine, now with Logan as part of it. In the last scene, Wade's friends gather, with Laura, rescued from the Void, and Dogpool, and Logan encourages Wade to make up with Vanessa. What comes next for the two of them is left open.