In Pretty Little Liars Hannah got hit by a car, and in The Perfectionists someone hit Caitlin with a car. Hopefully she survives and thrives as well as Hannah did after that incident. On Wednesday, Caitlin mistakenly believed she was flagging down Ava, but instead the mystery car sped up and plowed into her. It's reasonable to assume that Mason was driving the car, but there are actually some other potential culprits too.
Let's get the Mason theory out of the way first, because it is quite likely. Caitlin had just clobbered Mason in the cabin and stole his phone, so it would make sense that he was looking for revenge. He was also already in the woods, and we saw him open his eyes not long after Caitlin ran out of the cabin, so he could have followed her and mowed her over. But since Mason is the number one suspect here, that's actually a reason to look elsewhere. Showrunner I. Marlene King knows how to surprise viewers, so that's why it's worth looking at some other suspects too.
For the record, I don't actually think Mona hit Caitlin — but since she was the one who hit Hannah with her car in PLL, it's worth mentioning just on the off chance she went back to her old Mona ways. But here are some other more legit options.
Viewers saw how recklessly she drove Ali around in her trailer home. And, since she escaped (or was taken) from Ali's house, she was free to potentially do the hitting. There's not really a motive here, though, so she's not a top suspect despite her reckless driving skills.
The janitor told Mona that he thought Nolan deserved to me murdered, so Ray clearly has a twisted sense of justice. Perhaps he knows Caitlin's secrets too and thinks she deserved to get mowed down by a speeding car? Plus, Mona's program grouped him together with Caitlin and Ali, so maybe he's trying to take out the people who think like him. He can also see everyone on Beacon Guard so that could have helped him track Caitlin down.
She had just met with Ava in the woods, so she could have followed her out and sped by her in time to hit Caitlin. Dana's had her eye on Caitlin as a suspect in the Nolan murder for a while now, and she's not afraid to break the rules to wear down her suspects. Moments before the accident, Dana told Ava, "That's the beauty of not wearing the badge anymore, I can play the games however I want."
She seemed very angry that Caitlin lied to her about having been with Ali on the night of Nolan's murder. Perhaps she wanted to take Dana's investigation into her own hands?
Whoever Mason Was Supposed To Meet Up With
When Caitlin originally asked Mason to go to the cabin with her, he told her that he already had plans but that he'd get out of them. But then he was an hour late to the cabin. Maybe he brought those "plans" with him as backup and he/she went after Caitlin after seeing what happened to Mason.
It's a mystery for now, as is Caitlin's actual fate. But since there have only been a few episodes so far, it's unlikely Caitlin is dead or anything like that. Hopefully she'll be on the mend soon enough to try to catch whoever did that to her. Unfortunately Mason is a little too easy of an answer to be the only suspect, so Caitlin and co. have their work cut out for them to track the mystery car driver down.