I wasn't sure how I am supposed to tell false clues, but it all worked out fine, thanks to the number of active objects being very small. I've no idea what's the investigator's timer is all about so I lost my patience and used the last energy, I guess I was hoping it will speed things up, and this happened right when the investigator started to investigate what I think is the poison. Anyway, it seems like they won't be able to do it without me now.