Extract the answer to the following question from the movie plot. If the question isn't answerable, please output "Can't answer". Question: Who investigates a pair of murders? Title: Seven Movie plot: In an unidentified city of constant rain and urban decay, Detective William Somerset (Morgan Freeman) is preparing to retire and leave the horrors of the city. Before he retires, he is partnered with Detective David Mills (Brad Pitt), a cocky, young and short-tempered cop from Springfield, a comparatively small town. The two investigate the murder of a highly obese man (Bob Mack) who was fed spaghetti until a kick to his stomach burst him open. Somerset investigates the murder while Mills is given the murder case of Defense Attorney Eli Gould (Gene Borkan), with GREED written in Gould's blood on the floor. Gould was forced to carve a pound of flesh off of his body, and subsequently bled to death. The police captain gives Somerset an evidence container with three slivers of a plastic-like material found in the stomach of the obese man, which he was forced to consume along with the spaghetti. Going to the victim's house, Somerset finds three groove marks in front of the refrigerator and finds that the plastic-like slivers fit into them perfectly. Knowing the slivers resulted from the refrigerator being moved, Somerset looks behind it. He finds the word GLUTTONY written behind the fridge in grease, along with a note containing a quote from Milton's Paradise Lost. Somerset theorizes that a serial killer is basing his crimes on the Seven Deadly Sins, with five more to go.To give Mills and Somerset a chance to get along with each other, Mills's wife, Tracy Mills (Gwyneth Paltrow) invites Somerset over for dinner. While they are eating, a train passes by on the track nearby, making the building and all its contents and inhabitants tremble: the couple mention that that's why the realtor was so nervous for them to see the apartment quickly. After Tracy goes to bed, Mills and Somerset examine case evidence from the two scenes. They find a picture of Gould's wife with blood painted around the eyes. Realizing that this means she is supposed to spot something about the murder scene that nobody else would, the detectives...
Answer:
Mills and Somerset