How is “be in on the act” used?

In Everest (2015), one line is: “Yeah, it didn't take you too long to get in on the act.”

Which movie is “be in on the act” from?

The clip at the top of this page is from Everest (2015).

to be / become involved in an activity that sb else has started, especially to get sth for yourself

informal · Heard in 2 movies

Oxford100% of films
to be / become involved in an activity that sb else has started, especially to get sth for yourself
Yeah, it didn't take you too long to get in on the act.
And eventually, I even got them - in on the act. - Son of bitch!

Definitions from the Oxford Advanced Learner's Dictionary, 9th edition

Yeah, it didn't take you too long to get in on the act.

Said in 8 films · #1