Partners in an accounting firm are about to welcome a new young partner, a former military man who is engaged to the daughter of one of the partners. Things get complicated when he plays a cassette tape left in his car and it reveals a blackmail threat.
Antagonistic characters show up in the person of the math-challenged son of the other partner, and a woman somewhat jealous of the ring gifted to the engaged daughter.
When the jealous woman turns up shot, the gun is the new young partner's property, and the blackmail tape is found, things look bad for him ... plus his fiancé witnessed him meet a young woman at a motel!
As always, it's up to Jessica to find the unlikely clue which straightens everything out and discloses the real culprits, leading to an unusual heartwarming ending in what has just enough Christmas elements to live up to the episode title and theme.