Initially, I was 'only' a little interested because it was kind of slow to start AND I knew next to nothing about it except that a friend had recommended it. We have very similar tastes in shows, so I trusted them, obviously.
Anyway, I was hooked by about halfway through the first episode but I didn't realise HOW hooked I was until the episode ended and I went straight to the next rather than to bed like I should have.
The core conceit may not be anything new (most time-travel-hijinks movies and shows seem to stick to the same two or three ideas for some reason) but the cast, and the way the story unfolds, is just REALLY well done, especially Gabriel Howell as young Elias in the 'now' timeline. He's really only kind of an afterthought for most of the show but he absolutely comes into his own at the end, and absolutely steals the entire series in his relatively short but powerful spotlight moments. That being said, the rest of the cast are equally good, especially Amaka Okafor and Jacob Fortune-Lloyd as DS Hasan and DS Whiteman respectively.
A small part of me wants more of this, because it was so well done, but that small part is an idiot because 'more' would likely ruin it since they told a complete story. I guess I just want more of each of the cast?
