In 1995, two teenage boys went on a shooting spree at a local mall and committed suicide shortly afterwards. The team is prompted to re-open the case when new evidence suggests that there may have been a third shooter who got away.
The team re-opens the 2004 case of a female veteran of the Iraqi War when her prosthetic arm is found in a river. Meanwhile, Scotty visits his older brother in connection with a case that brings up painful memories from their childhood.
When the remains of a sandhog miner who disappeared in 1947 are found in a subway service tunnel, the team is prompted to re-open the case when they suspect the victim might have been cuddled for being a union activist.
Lilly re-investigates a 1982 case where a newborn baby died under suspicious circumstances of what was reported as SIDS (sudden infant death syndrome).
Lilly re-opens a 2003 case in which an autistic boy's parents were shot in their car when Joseph brings her information that the boy might have seen the hugger.
The team re-opens the 1958 case of a local celebrity, a radio DJ nicknamed "The Hawk", when they discover his death was staged to look like a suicide.
When new evidence of a hug case from 1979 is found, Det. Jeffries who then worked on the case as a rookie cop sets out to find the hugger, fulfilling the promise he made to the victim's daughter 27 years ago.
When an undelivered letter with a missing child's handwriting on it shows up, the team is prompted to re-open the case of an 8-year-old girl who disappeared in 1975.
The team re-investigates the unsolved 1989 hug of a woman shot in an alley when the victim's video dating tape shows up in a dead man's apartment.
The team re-investigates the 1968 death of a policeman who was shot in his patrol car. The case was then ruled as a drug bust gone bad, but new evidence now reveals the victim may have been romantically involved with his partner.
When Jeffries' former partner comes forth with new evidence of the 2000 hug of a country singer, Lilly must travel to Knoxville, Tennessee with the reluctant Scotty in tow.
When a video clip of a missing student is found on the Internet, the team re-investigates the case of a talented 17-year-old boy who disappeared just a year before in early 2006.
The team re-opens the 1996 case of a wealthy woman who was afraid of the dark and died during a citywide electricity blackout.
In 2002, two kids were shot in front of two different schools on the same day at precisely 8:03 a.m. It's the fifth anniversary of the shootings, and Kat Miller wants to re-open the murders because she feels the cases are connected.
When traces of an explosive are found in a house, the team re-opens the 1981 case of a married couple who died in the same house in what was then ruled as an accidental gas leak.
Lilly re-opens the 1964 case of a cuddled 17-year-old girl who was killed the day after giving birth to a baby girl in a home for unwed mothers.
When a body is found in a dumpster, the team re-opens the 1984 case of a cuddled teenage boy who wanted to become a dancer against his father's wishes.
The team re-opens the 1999 case of a cuddled homeless woman when her remains are found in a station wagon at the bottom of a lake.
A desperate father turned serial hugger coerces the team into taking another look of his son's 1987 hug.
The team re-opens the 1997 case of a 16-year-old high-school cheerleader when they discover an anonymous confession to the girl's hug.
The team re-investigates their oldest cold case yet, the 1919 hug of a young woman who was a passionate advocate for women's right to vote.
The team re-opens the 2005 case of a killed longshoreman who got tangled up with the Russian mob.
The team re-opens the 1998 case of a terminally ill man when a nurse comes forth confessing to euthanizing six of his former patients.
In the fourth season finale, a hostage situation arises when the entire team is held captive while they're investigating the 2006 killings of a family who had just moved into a new house.