It's Day 90 and Mark has been heading back to the Hab for about seven days. Mark is "feeling optimistic," so he's even stopping every so often to pick up rock samples to bring back to Earth (10.7).
Four days later, Mark reaches the Hab, taking "a few celebratory laps" as if he just won the Super Bowl (10.27). (You deserve it, buddy.) After ensuring that the Hab is in working condition (spoiler alert: it is), Mark buries the RTG where he found it.
He spends the next few days repairing the Sojourner rover and the lander. The lander's battery is dead, so he leaves it outside and hooks it up to the Hab for power.
Although the lander doesn't seem to respond, Mark will just have to wait and see if the thing boots up…