What a terrific murder mystery. As someone who enjoys climbing, I was initially bothered by the unrealistic climbing techniques shown. But if they were truly experienced climbers, how could they avoid serious injury before attempting anything difficult? (And from a filmmaking standpoint, with climbing being so popular, surely it wouldn't be hard to get someone from a local gym to point out that those techniques are wrong! There are also other unbelievable things later on…) The explanation, of course, is that what we saw was simply **Becky’s version of events!!!** Then all the inaccuracies make sense because that’s how she convinced the authorities that the “accidents” happened — due to carelessness and a lack of skill. I think Becky discovered she had been cheated on and then planned to get rid of her partner by messing with the gear placements or – as shown in the film but with malicious intent – loosening the rope. No one else knows how secure those placements were, or if they were tampered with; Hunter was too far away, busy descending! This explains perfectly Becky’s year-long depression because even if it wasn't fully planned, her actions naturally led to a deeper sense of guilt. Then there's the fact that we can never truly know whether Hunter initiated the tower’s collapse. Maybe Becky saw Hunter was living without any remorse and felt another urge to kill, suggesting a sensational YouTube/Instagram trip to lure her along! Even though the film portrays Hunter as kind at times, it’s entirely possible that she is simply presenting a carefree persona online! (which might make her more vulnerable in Becky's eyes). So Becky could be manipulating people into seeing her victims as compassionate sweethearts. Finally, the biggest clue suggesting the final accident was premeditated (and perhaps intended by the filmmakers) is that when Becky went back for Hunter’s body to drop the phone, she instinctively clipped the carabiner to the most stable point – the ladder that hadn't broken yet!!! (and the film really highlighted this). Why wouldn’t Hunter do that when retrieving the bag??? It’s not just poor climbing; it doesn’t even make sense! We were all yelling about how foolish Hunter was during the bag sequence, and now we know these are likely fabrications recounted by Becky after the accident. Also, some observant Chinese filmgoers noticed a “mistake” on the poster where the ladders appear to be failing while Becky is at the top and Hunter is still climbing! Perhaps this is a hint from the production team ;) Anyways, it’s just a theory :p I probably watched too many Asian soap operas.

Source on TMDB