When the ship got to Mars, everything was fine until a bad windstorm came across. NASA ordered for everyone to leave mars imminently if the wind went over a certain speed. The commander ordered everyone to go to the ship in case of evacuation, but when Watney was going, he got blown away and no one could find him.
I may not die after all!
After Watney got left behind, he did an inventory on all of the food they had, and realized that he doesn't have enough to keep him alive for any more than 400 sols. So he used is botanist skill and started growing potatoes by using lots of Martian soil and his own poop as food for the soil.
Ares 4 Landing MAV
After thinking for some time, Mark Watney remembered about the pathfinder, and where it was. It is used to talk to NASA.
Thank the Lord your back safe.
After spending many sols fixing the pathfinder, it is finally working and communication with NASA! Once NASA got through the "Are you okay?" stage, they explained how they plan on getting Watney back to Earth.
After talking to NASA, they told him that his crew is going to go back for them, and that he needs to get to the next mission (Ares 4) landing area by a certain sol.
Once the ship got to Mars, Watney was able to get on the ship in one piece and alive. Everyone talked about what it was like to be left on Mars. After they got back to Earth no one could leave Mark Watney alone.