Minka Kelly as Detective Valerie Stahl, another detective serving under Captain Maldonado, and a love interest for Kennex. She is a Chrome, a human genetically engineered for beauty, excellence and success. Other Chromes consider her choice of profession to be a waste of potential.
The first episode does not begin with the death of a Chrome, but episodes 10 and 12 of the series do:
Two "chrome" (genetically engineered) girls are killed by a new designer drug, which is related to a previous accidental drowning of another girl. Kennex and Stahl (a "chrome" herself) investigate the case, which leads them to the Mendel Institute, where many students, except two, are "chromes". When they find a sample of the drug, the pharmaceutical printer used leads them to a former Mendel Institute student, who acknowledges making the drug, called "Vero", but swears the printer was hacked to create the fatal doses. The clues finally lead them to the mother of the first girl—who had killed herself after taking Vero—and who hired the hacker for revenge. Meanwhile, Kennex uses drugs and a black-market Recollectionist doctor to try to remember more things about his traitorous ex-girlfriend Anna Moore and the ambush where he lost his leg, despite Dorian and Maldonado's warnings. He finally remembers a detail which leads him to discover his home had been bugged.
After a healthy chrome is reported to have died from natural causes, Detective Stahl suspects foul play. Upon further investigation, they find that the dead chrome has the DNA of seven other victims all with good looking facial features. Kennex and Dorian are called in to track down a serial killer (Michael Eklund) who has been using a nanobot surgical system to take facial features from his victims and transferring them to his face for the woman he loves, who he has been communicating with via online conversations (Only to learn upon meeting her that she is blind). Kennex makes a move and is about to ask Detective Stahl out for a drink, only to find out that he is too late.
However, Wikipedia's talk page mentions that Fox aired the episodes out of order, so it's entirely possible that you saw one of those first.