I enjoyed this but there are a few suggestions i would make. First off the font for the subtitles should be neutral and clean, and most importantly, easy to read! The subtitles don't need to be styled to suit the aesthetic of the film, they just need to be readable. Similiarly they should be consistent, the voice acting should make clear who is speaking. If you want it to be clear even for the deaf, then try using slightly different colors.
You use filters, which is a nice touch and adds some character to the animation. However you use them too often and too obviously and it becomes annoying. Try to use the overlays subtly or not at all.
The character design was decent i thought. The beast in the cave was really cool! The music was all good too, but the sound design obviously needs work as people can't hear what's being said. Either that or you need a better voice actor or microphone.
My favorite thing was the plot! Really enjoyable script, interesting dialogue and a creepy atmosphere. Good pacing too! Overall i thought it was a good flash, keep it up!