It's a sci-fi series, a very popular spin-off from another, very popular sci-fi series which has been going on for much longer than these series usually last. They have two "chief" doctors clashing in the lab; the guy who has been there since the beginning of the series, who just came back from the dead (although with complications), and a pretty girl, loved by the fans, played by an actress who had a very popular role in another sci-fi series...
Which series am I talking about?