Diagnosis: Death (2009) on Netflix

Plot summary

A clinic that tests experimental medicines on willing volunteers has taken on a weekend group, among them Andre Chang, an unethical teacher, and Juliet Reid, a bookish teenager. The two of them meet there for the first time. Staff keep the doors locked for the length of the trial, and the drug that the volunteers are given brings hallucinations, so it is unclear whether the clinic is haunted or the medication is at work. Andre and Juliet cannot rely on their own eyes, and with the trial holding them inside, working out what is going on is the only way they see to get free.