An Asian woman watches people dancing at a club. She answers her cell phone, but we can't hear over the music. She leaves and is run over and killed.
She is identified as Michelle Kim from ID. Don wonders why LAPD isn't handling it, but Colby says Kim used to work for Chinese consulate as interpreter.
There are lots of bars in the area, and they figure the driver was drunk.
Charlie tells Amita he's using differential geometry to perfect the chocolate chip cookie for Senior Ditch Day. He figures cookies will prevent his office from being ransacked like last year.
Amita points out an article Larry published on zero point energy and quantum cosmology. Amita is surprised that Charlie didn't know, as she assumed Larry asked him to collaborate.
Kim's father was a former Chinese diplomat who retired in 1997. A background check happens to be filed by an old Army buddy of Granger's, Dwayne Carter. He saved Granger from an RPG while they were both in Afghanistan.
Don finds Charlie at the FBI offices looking at Larry's file, using the FBI's ability to get through firewalls. Charlie, apparently feeling the need to do something, asks Don if he needs help on Michelle's case. Don doesn't think so but Charlie grabs the file anyway.
A bartender remembers seeing Michelle using a cell. It's traced to a pre-paid cell. They also find out that she had a lot of cash in her bank account.
Charlie admits to Amita that he thinks Larry's paper needs his assistance. She points out that Larry didn't ask for his help.
Charlie compliments Larry on his paper and asks who collaborated on the math. It was Brian Stromsborg. Charlie says Stomsborg is good, but Larry suspects there is more to Charlie's visit. Charlie admits to wondering if there was a reason he didn't come to him. Larry says he just felt like branching out and felt the need to stretch himself a little. Larry has to leave and excuses himself.
Don and Megan talk to the Chinese Consulate. The man says he really didn't know Michelle that well. Meanwhile, Charlie concludes Michelle was murdered, describing the path of the moon and saying how the knee travels in a similar cycloid while we walk. The marks on legs show the bumper was rising on impact, meaning the impact was intentional.
Techs find a lot of internet porn on Michelle's laptop. Charlie thinks there is hidden information in the pixels.
A passcard found near the scene has Michelle's prints all over it. It turns out to be for a building garage. The attendant says she has had an apartment there for about 2 years. There is a security camera in the lobby. The apartment is found to have no food.
Charlie gets Larry to help look for the info hidden in the photos. They find something in the eyebrows and on a photo of Michelle on her lips. There are names of 2 people who were to be witnesses against Jason Ming. But the witnesses, Terry Evans and Richard Freeman, were murdered. Ming was arrested for selling laser gyroscopes to North Korea. The Federal witnesses were in a sealed indictment. It seems there must be a mole in DOJ.
Colby confronts Dwayne who was seen in the lobby video. His face wasn't seen but they were trained to put sunglasses on back when approaching target. Dwayne says Michelle approached him after he did the background check and they wound up sleeping together. He admits he had a pretty good idea that she was a spy.
Colby is furious. As an excuse, Dwayne mentions that things went bad with him and his wife after he got back from Afghanistan. But he insists the affair was all there was.
Charlie bemoans to Alan about Larry not collaborating with him on his latest paper. Charlie thinks the good paper could be great if Larry would accept his help. Alan tells a story about seeing something that could be improved on a plan designed by boss, but he didn't say anything.
Although there are only cameras in the lobby, Charlie says advanced symmetry analysis can be used on faces. He relates it to Rubik's Cube. There happens to be one in the office.
Megan reports that an SUV was found in a chop shop that matches the description of the hit-and-run. Colby goes in to pose as a customer and gives coded info to David. Then David leads a raid on the shop. Tyler grabs Colby, but Colby tells David to shoot Tyler. While they seem to be arguing, Colby grabs Tyler's gun. David is concerned how Colby let himself be grabbed but Colby insists he's fine.
Charlie presents the face of the guy who showed up 8 times after the 24 times Michelle used the apartment. It's Dwayne. Don confronts Colby. He admits he had a feeling that it was Dwayne on the tape. Colby insists Dwayne being there has nothing to do with the case. Don says that's not true. Colby says Don isn't perfectly clean, pointing out the time Megan was kidnapped. But Don takes Colby off the case.
Megan and David go to search Dwayne's apartment while he's swimming in the pool. Dwayne finishes much sooner than they expect. They hide when he comes in and they manage to get out when he goes to other room.
Larry goes to talk to Alan. Larry says Charlie's work at FBI is increasingly consuming Charlie.
David reports that bank manager inadvertently tipped Dwayne off that the subpoenas were being served on Dwayne's accounts. They figure he'll run. But Don wonders if he'll hang around for one last score. Megan notices unexplained appointments on Dwayne's PDA, and Charlie analyzes the meeting places. They all are within a circle but it's assumed that no meeting places will be duplicated. Amita works to predict where it will be. Charlie says it's like predicting where a tree will branch based on previous branches.
A number of locations are staked out. They find a very short meeting at a plaza where something is exchanged with a Chinese man. Dwayne becomes trapped in a cab in a tunnel. But it's a dummy.
Megan thinks Don should let Colby back on. Colby, on his own, finds Dwayne about to depart on a boat. Dwayne says he was only giving useless information to the Chinese and every dime he was paid went to his son. Dwayne says Michelle started blackmailing him. Dwayne reminds Colby that he saved Colby's life once.
Colby reveals he's wearing a wire. Dwayne pulls a gun and demands the tape. But then they hear sirens approaching. Apparently, Colby wasn't on his own. Don warns him if he ever does anything like this again he'll go to jail.
Larry asks Charlie for help with paper. Charlie admits he already read it and says it's a work of genius, but it would have benefited from the work of 2 geniuses.