The BAU is called to Pittsburg to investigate two strangulation murders.  They eventually discover that the Unsubs (who are married) have been attempting to get their marriage on track by targeting single people who won't be missed, killing them, and then having sex right afterward.  When Garcia finds out that they've been seeing a marriage therapist, Reid and Morgan rush to the therapist's office and catch the Unsub right before he can finish strangling her. Afterward, Garcia and Morgan bump into each other with their dates on Valentines and decide to share a table and have a milkshake together.