Hi, new to the thread. I just watched the first episode. A minor thing, but I think it's going to be important somehow (this where I'll open my mouth and be proved wrong). When the detective was in the attic, he picked up a swimsuit/lingerie brochure and the female detective joked about 'titillation'. I think it belonged to the murderer.
The guy in the basement has keys to all the flats and is def creepy, but is too obvious. Is that his daughter living in his flat? Why is she like a prisoner and why is she wearing old lady clothes? Did you notice she had to have his dinner ready as soon as he got in.
The house is really creepy. The exterior is a house in Greenwich, but the interior was built in a studio because the production designer had the house in her head, but couldn't find one that met up with her thoughts...so her team built it.
Overthinking...