It's interesting. The story line is a bit slow to get start, but after about episode 3, I just kept going.
IDK if BBC shows can get Emmy nominations, but the lead actress is flat out amazing. So far, she's playing 3-4 regular characters (Sarah masquerading as Beth, Alison, Carmisa; not-regs: Beth, the Russian, the German). The thing is, each character is completely infused with their own body language, accents and personality. Granted, they can do a lot with the hair and clothes and they do, but it's the actress that is just killing it. Honestly, I have absolutely no problems telling each character apart at all.
Basically Sarah, who is not a very good at being a person, finds a woman who looks exactly like her, minutes before that woman commits suicide. Since Sarah isn't a very good person, she lifts that woman's bag, discovers Elizabeth Childs, and infiltrates Beth's life. In doing so, she discovers that Beth was ac cop, has a HOT boyfriend and is part of a ring of Orphans that are all genetically identical and are trying to find out where they came from. It takes off from there. The surrounding characters are very good as well.
I recommend. It's nice in that it is a science fiction show, but it doesn't rely on aliens or zombies or vampires or flashy tricks. It's very "human dealing with technology problems". Reminds me of something Isaac Asmiov would've written.