Credit to the walkthrough guys for the description:
Back to Fiona. You'll meet a pretty cool bandit dude, who'll end up selling you a mask (I just took the free ones) and setting you up as racers. Dubstep bandit man will announce that the race starts in 30 minutes in the middle of your conversation with Vaughn. Time to win the race for the case. You'll meet your new teammate that tries to kill Vaughn, and the race will start as you switch back to Rhys.
Do some QTEs until Vasquez offers you a deal to get your old job back and half of the money, if you blame Vaughn. Accept his deal for only negatives, reject it for only positives. Back to more QTEs... a ton of them. It will continue way into your time back as Fiona as well. Eventually, Zer0 will cause some craziness and Felix will end up with the case. He betrays you, because of course he does. Once you wake up, there will be some more things to click. Then, tell him "Don't open it" as your choice between two options or you will lose him as an ally and a bunch of money at the end of the game. This will also prevent you from being able to have the option to buy some other allies as well.
Then, you will be Rhys again. Start walking forward and a cutscene will play where your old buddy/son will make his valiant return!
Here is a video of the chapter:
Credit to DanTheMan.