Great question! The key differences are:
- Caught in the Rain (CitR) uses a standard deck of playing cards to act as not only a timer for the mystery but also the clues themselves compared to an accumulation of progress points and asking the system if you've done enough to solve the mystery in mythic.
- CitR creates a framework of scenes specifically designed to lead to finding clues compared to Mythic's general scene system that is applied to its mystery rules.
- CitR uses dice resolution rules with fail-forward mechanisms built into it to ensure that the mystery and the narrative keeps moving forward even if it becomes more dangerous for your investigator.
I love mythic and I still use it as my go-to GM emulator. Tanya is a big inspiration for my solo designs :) .