As the Walkthrough says: "Get out of your escape pod and you'll receive a call. Now run towards the massive monster and do your QTEs. Head towards Vallory, then open the caravan. Not long after, you will be grabbed by Mr To Kill a Mockingbird. You can choose to kill him or let him rot. I just shot him (with fire, but it shouldn't matter). Time for some conversation with Vallory. No matter what you do, it does not end well for her. You'll have to man the big-ass rocket launcher. It won't work out at first, but your sister will soon be there to help."
Credit to the gamers who made the Walkthrough.
IGN gives a very well description of what goes on in the chapter of that Episode and how to advance the game: https://www.ign.com/wikis/tales-from-the-borderlands/Chapter...
Credit to IGN for their descriptions with pictures.
Additionally, here is a video from YouTube that walks you through the chapter:
Credit to VGFAQ for the video.