Vogler, Memo From the Story Department:
About three-fourths of the way through the story, the hero is driven to complete the adventure, leaving the Special World to be sure the treasure is brought home. Often a chase scene signals the urgency and danger of the mission.
The hero is driven to complete the adventure by either returning to the ordinary world or continuing to another destination. The road back signifies the shift into Act 3 where the hero must deal with the consequences of confronting the dark forces in The Ordeal. Often this stage includes a chase scene to reinforce the danger and urgency of the mission.
Batty - Movies That Move Us:
Physically, the protagonist must leave the Special World and return to the Ordinary World. On the Road Back he overcomes further physical obstacles, and may even leave behind objects or people ‘collected’ from the journey. The protagonist may experience physical pursuit on his way back to the Ordinary World, but if so, he will be helped by the tools provided by the Mentor. Pursuit suggests that although the protagonist may wish to remain in the Special World, the physical environment can no longer accommodate him; so, he must leave. The Road Back physically challenges and tests the protagonist, but his will to overcome further obstacles is evident. What previously seemed physically unachievable is now fully achievable, thanks to the physical transformation that he has undergone.
Vogler, Memo From the Story Department:
On the physical Road Back, the hero inevitably is tested on the inner plane with a New Challenge requiring Re-Dedication. Physical chases, escapes and rescues may mirror inner temptations and backsliding into old patterns of behavior, or there may be new, unexpected challenges to the hero's intention to change. The world may refuse to accept the hero's new status and try to drive him back to his old condition.
Palmer - http://www.crackingyarns.com.au/2011/04/04/a-new-character-driven-heros-journey-2/
Step 10. Desperate (Road Back)
In the last sequence, the Hero was feeling pretty good about themselves because they’d just climbed their personal Everest, but in this sequence they have a daunting realisation: now they’ve got to get down.
This is where some complication occurs that makes the attainment of the Hero’s original goal seem much more difficult or downright impossible.
But it’s not just about plot. It’s not just about being in a dire situation. If you want to tell a great story, at this point it can help to present the hero with a dilemma – to put them between a rock and a hard place.
In an earlier post, I explore this crisis in great detail, but in summary it’s about forcing the Hero to choose between what they want and what they need.
Very often, the choice is between a material goal and love.