When an undelivered letter with a missing child's handwriting on it is found, the team is prompted to reopen the case of an eight-year-old girl who disappeared in 1975.
When a postman dies in his home the homicide squad find bags of undelivered mail from 1975. In one of those bags is an undelivered letter from a missing 8 year old girl to her best friend which could have saved her life. The squad open up the case of Melanie Campbell who disappeared in 1975 from her bedroom. Rush and Scotty go to visit Melanie's parents, Melanie's mom believes her daughter is still alive while her father just wants his little girl to be buried. Will and Miller then go visit Terell Pierce, who was one of the main suspects back in 1975, because of racism and Cherise Pierce who was then Melanie's best friend and who the letter was for. Will and Miller find out that when Terell and Cherise moved into the all-white neighbourhood it came with a lot of anger and frustration as nobody wanted them living there, but Melanie liked Cherise and told her how fireflies are really fairys who live in heaven, from then on they were best freinds. Will and Rush then interview Hank Wilson who was the leader of the mob who wanted Terell and Cherise out of town, he said that he had nothing to do with Melanie's disspearance and that they should talk with Wes Floyd who was a property developer who wanted all the whites to move into a new neighbourhood so he could make a profit. Scotty and Nick then interview Wes who says he wanted the Campbell's to move out the neighbourhood and made a menace of himself but did't have anyhting to do with Melanie. He said that if he wanted somebody to talk to they should talk to the kids of the neighbourhood because they really didn't like Cherise and Melanie being friends.
- Kathryn Morris as Lilly Rush
- Danny Pino as Scotty Valens
- John Finn as John Stillman
- Jeremy Ratchford as Nick Vera
- Thom Barry as Will Jeffries
- Tracie Thoms as Kat Miller
- John Aylward as Norman Campbell (2006)
- Dee-Jay Daniels as Terrell Pierce (1975)
- David Henrie as Dale Wilson (1975)
- Bobby Hosea as Terrell Pierce (2006)
- Jenny O'Hara as Frances Campbell (2006)
- Judith Scott as Cherise Pierce (2006)
- Gabby Soleil as Cherise Pierce (1975)
- Savannah Stehlin as Melanie Campbell (1975)
- Shannon Sturges as Waitress/Melanie (2006)
- Richard Steinmetz as Dale Wilson (2006)
- Johnny Kastl as Wes Floyd (1975)
- Becky Meister as Frances Campbell (1975)
- Wolf Muser as Wes Floyd (2006)
- Michael Eric Strickland as Hank Wilson (1975)
- Don Yanan as Hank Wilson (2006)
- Unknown actor as Norman Campbell (1975)
- Instead of putting the box with all the other closed cases, the team instead gets rid of the box, because the person never died. This is one of the five occurrences in the series in which the victim was found alive (the others are The House, Joseph, The Road, Ghost of My Child).
- The Smashing Pumpkins' version of the song "Landslide" was used in the finale of the season 3 episode Detention.
- America "Tin Man"
- Stevie Wonder "Living For The City"
- The O'Jays "Love Train"
- Gladys Knight "The Best Thing That Ever Happened To Me"
- Earth, Wind and Fire "That's The Way Of The World"
- Closing Song: Fleetwood Mac "Landslide"