The Alchemy Murder Case File 3 - S1-E8
Plot hole: The locked room mystery is original, but besides the fact that it requires melting part of a door on the spot and being able to repair it absolutely flawlessly so that nobody would notice any bump and discolouring and irregularity when they check the lock later investigating the murder, it also requires them to do it in total silence so the other guests don't notice, and part of the process shown involved cutting through it with a screwdriver and bashing it with a hammer - they show that and there's even a loud sound effect for it. (00:18:00)
