How is “start back” used?

In The Secret Life of Walter Mitty (2013), one line is: “I guess, just start back from the beginning.”

Which movie is “start back” from?

The clip at the top of this page is from The Secret Life of Walter Mitty (2013).

I guess, just start back from the beginning.

7 作品で登場 · 1 本目

to begin to return somewhere; to begin again from an earlier point in a story or explanation, especially the beginning

7 本の映画に登場

オックスフォード映画の 67%
to begin to return somewhere
Then we should start back. No, if that ship can still fly, we need it.
編集映画の 33%
to begin again from an earlier point in a story or explanation, especially the beginning
I guess, just start back from the beginning.

定義：Oxford Advanced Learner's Dictionary 第 9 版