So Marchlands is over, but who drowned the cat?

I have just watched the last episode of Marchlands, which unusually I managed to see the whole series of without forgetting to record it or letting so much time elapse that it was no longer available ITV's equivalent of iPlayer.

If one makes allowances for it being a ghost story, it avoided annoyingly implausible endings.

Yet I hate loose ends in plots. So who drowned the cat in the garden pond in episode 2 (or was it episode 1)? Amy, the daughter of the household was suspected, but she blamed it on her imaginary friend Alice.

As a result, Amy was thought to have a personality disorder and was referred to child psychiatrists etc. However, Alice was not imaginary, but a ghost and at the end of the final episode shown to be a benign not an evil one. And Amy's family accepted that Alice was real so their daughter was not a budding psychopath, and all was well.

But in that case who drowned the cat? My experience of moggies is that they don't just fall into ponds, but the cat killer was never exposed. Perhaps this is just paving the way for a second series.