Joe Wheeler is a former hedge fund manager who holed up in a bunker in the Sonaran Desert for a year in order to escape from the apocalypse that occurred. Eventually, rations ran dry and Joe was forced to leave.
After getting the lay of the land and joining up with Alice Ivers and Isham Seely, Joe decides to do one of three things: amass a vast amount of money, recruit 80% of the Survivors in the desert, or find love for the first time in his life.
Outcome 1 - Money:
Largely helped by the El Dorado questline, Joe manages to end the events of Survivalist sitting on top of a large amount of money, knowing that he will be able to live comfortably by trading with other communities in the desert, and so he lives peacefully.
Outcome 2 - Power:
Deciding that his small group of Survivors isn't enough for him, Joe scours the whole desert, enticing other groups to join the Survivalists for a better and more secure life, and terminating all those who stand in his way. Regardless, in the end, Joe stands tall as King of the Sonaran, with a huge army behind him, ready to wreak havoc on anything or anyone who stands in his way.
Outcome 3 - Love (Canon):
Whilst juggling vital survival needs, relationships with other groups and the threat of the infected, Joe starts to build up a romantic relationship with Alice. He does a lot of activities with her; jogging, shooting, collecting flowers, and helping out with the Insulin issue. Despite Alice's concerns that she will eventually succumb to Type 1 Diabetes, Joe will always remain adamant that she will survive with him. Eventually, the pair become lovers, and everything is proceeding well. However, when the Survivalists, Joe and Alice included, siege the F.E.M.A. base, Clara Allison reveals that Joe indirectly caused the infection due to failed prototypes of erectile dysfunctions drugs. However, the matter is made worse when it is revealed that Alice was being experimented on by F.E.M.A. scientists, and she was known as "Patient X." This was also the case for other survivors such as Lou Marchbanks and Charlie Cashman. This meant that she was a Living Infected: having the appearance of being alive, but actually infected. In the shock and angst, Alice flees the compound and leaves the Sonaran Desert. Joe, heartbroken, calls upon Isham for help. After much deliberation, the Survivalists leave the Sonaran Desert and head to Vancouver, to find Alice and get answers.
This is likely where the sequel will take place.