Good Cop. Dog Cop. After the demise of the team's much-loved partner, Detective Charlie Hudson, Mark accepts an offer to join the St. John's police department and work with the extraordinary dog, Rex. From saving a runaway witness from a hired assassin to investigating the death of a respected gin distiller, only Rex's razor-sharp instincts combined with the SJPD's brilliant insights can solve a groundbreaking set of cases. Guided by Mark's investigative abilities, Sarah, Donovan, and Jesse bring together their own unique areas of expertise to ensure the Major Crimes division stays in peak form as they face unpredictable threats.