Munch makes a bold move, Indira and Witt have questions, Wayne takes a fall and Gator disappoints.
Ben leaps back to 1692 -- the farthest he's ever been -- where he finds himself on trial for practicing witchcraft. With limited records online, the team must race to save him before he's put to death.
After a high-stakes homicide case falls apart at trial, Katsumoto asks Magnum to help him stop a killer from walking free; Higgins helps Jin Jeong with a mystery of his own.
When a British Air Force weapons test goes disastrously wrong, DCI Amy Silva is called in to investigate. With seven military personnel dead, two from Britain's allies in the Middle East, Amy finds herself caught in the crosshairs of a fraught international incident. The Air Force think they have the guilty party in custody and push for Amy and DI Kirsten Longacre to close the case. But Amy isn't convinced.
Amy and Kirsten are battling for their lives against a ruthless armed killer. They manage to escape. Following new evidence, the case takes a turn. Amy must go to the Air Force base in the Middle East. There, she learns someone on the base was complicit in the attack. Meanwhile, in Scotland, Kirsten hunts down Chapman's killer, determined not to let her pregnancy get in the way of her mission.
Following the stabbing of an officer on the base, Eliza warns Amy to get control of her investigation. Amy must find the traitor in the ranks of the Air Force. Kirsten, now working with MI5 partner Ramsay, uncovers key evidence linking a squadron member to the attack. With the force running out of leads on Chapman's killer, Kirsten follows a hunch. Amy takes a grave risk that puts her in jeopardy.
Against the backdrop of the biggest event in New York City's history, Bertha reconsiders her loyalty to the Met. Meanwhile, an engagement celebration leaves Marian with doubts, Peggy strives to make a difference in Brooklyn, George strikes a deal with Mr. Henderson, Oscar makes an alarming discovery, and the van Rhijn household reels as Luke's health deteriorates.