The fiancé of a fireman asks Lilly to help prove that a convicted felon, about to be paroled on an unrelated crime, is responsible for the murder of the fireman's first wife. The young mother was killed by a homemade bomb shortly before she was to testify in court against a man who exposed himself to her.

When the remains of a young black man and a white woman are found under the foundation of a building, Rush and Valens discover that not only did the two go missing in 1969, but that they may have been killed professionally for their work in an underground abortion clinic.

Lilly investigates the deaths of a married couple who perished in 1981 when a supposedly accidental gas-leak explosion set their house on fire. The case is reopened when fragments of a bomb are discovered at the house during renovations. Back at headquarters, Stillman takes care of his 4-year-old grandson.

The team re-opens the 1999, 2001, and 2003 pipe bombing incidents that killed two and blinded one victim. The serial bomber is still on the loose and ready to strike again as he missed his latest target.

A drug addict mother, who lost her son in an apartment fire in 2005, comes forth claiming she just saw the same child in the park.

Lilly and the team attend a colleague's wedding and are persuaded by Jeffries to investigate whether the bride killed her former fiancé two years earlier - just hours after he called off their nuptials.