Dark - it's a sci-fi mystery show with
Small spoiler for like episode 3
time travel
with a really captivating and intriguing plot. It's available on Netflix and is originally German, but I feel the English voice actors did a great job for the most part. It's very intricate and tbh a bit confusing the first watch with how many characters there are. I honestly started keeping notes on who everyone is! The soundtrack is amazing, it's so thematic. I watched with my mum and she refused to walk the dogs at night afterwards without me there because the soundtrack is so intense and disturbing for some of the scenes. I highly recommend this.
To a lesser extent, I also recommend 1899 by the same team. It's also really interesting and cerebral, but was unfortunately cancelled after one season when it was starting to get interesting. The English dub does lose out a bit though because in the original there are three or four languages spoken and it turns into an important plot point as to who speaks what language. I didn't even realise they were speaking different languages so I was just confused when that happened.