Anyone else think it was the cat?
Sure he was playing up the cute and cuddly bit for the cameras, but it was that very thing that tipped me off, he just was too innocent. I really can't believe it was the _____ (the person who the movie says was the killer). The cat was the only one who could move about with no one noticing.
Look at the way he played with the yarn. Seems like a typical cat at first, but look closer, it's all right there in his eyes. And think about when Emily Brent is murdered, who's there? Not the _____. No. It's the cat. All he had to do when everyone came up the stairs was act like he was playing with the yarn and no one payed him any attention. But it was clear to me that the director was telling the audience who the real killer is. It was rather obvious symbolism. He was playing with the yarn just as nonchalantly as he was playing with these peoples lives.
Remember, in murder mysteries the killer is often the one you least expect. My guess is that "puss" had been given one too many baths and required retribution to repair his dignity.