And Those We Left Behind - S4-E6
Continuity mistake: While beginning to take the radiation readings of the Jeep during his time jumps, Peter has a wedding ring on his finger. After cutting away and back again, the wedding ring is no longer on his finger. (00:15:15)
Brave New World: Part 1 - S4-E21
Continuity mistake: This is when Peter and Olivia are discussing different Boston's suburbs as their potential new home. The sun is on the right side of Olivia's face in one shot. In other shots, it isn't.
Brave New World: Part 2 - S4-E22
Continuity mistake: The left side of Peter's face is alternately bathed in sunlight or not throughout the scene when he and Walter talk in front of Olivia's hospital room.
Answer: He helped his father evade capture, impeding the investigation.