After Barton's departure from Millgate is blocked by a permanently jackknifed logging truck obstructing the only route out of town, he discovers that Christopher remembers the town's erased past.
After Barton's departure from Millgate is blocked by a permanently jackknifed logging truck obstructing the only route out of town, he discovers that Christopher remembers the town's erased past.  This could be rephrased as:

* After Barton's exit from Millgate is thwarted by a perpetually stalled logging truck blocking the sole path out, he finds that Christopher recalls the town's forgotten history.