New York City, 1950. Viviana Valentine and Tommy Fortuna have a lot of resolutions for the new year--whether it's continuing to build up their detective agency or planning their wedding, the two are looking forward to the future. On their way to Times Square to celebrate, the two witness a brutal stabbing. When Tommy tries to chase down the culprit, Viviana tries her best to save the man. She's unsuccessful, but Viviana hears his final words: a whispered apology to an unknown friend.

Clues are hard to come by, with the only leads being the fraught last words and a few nondescript matchbooks in the victim's overcoat. Their investigation is halted when Detective Jack Lawson of the New York Police Department arrives, immediately ruffling Viviana's feathers and bumping chests with Tommy, who he nearly arrested for murder just months earlier. The two know there's more to the story, but there are other pressing matters at hand.

Clients are clamoring to get the detectives to work on their cases: a man is being blackmailed by a criminal who only writes in code, Tommy's old friend needs his fiancée tailed, and an investment banker has mysteriously vanished. To add to their workload, Viviana knows something strange is happening at her boarding house. Will all of this--plus planning for a wedding--be too much for one Girl Friday?