Robin and Ted reminisce about past relationships as they search for a drunken Barney on the day of the wedding. Lily and Marshall come to a resolution. Barney befriends two men who are eager to meet women.

The daughter of a senator in Mexico is kidnapped by a cartel; Lillian uncovers a connection between her father (Peter Coyote) and the cartel.

Marty deals with hip-hop clothing moguls, who have divergent attitudes and plans for their company; Jeannie defines the role she will play in her new position; Clyde goes through some personal hard times and turns to Marty for help.

When Joan revisits one of Sherlock’s cold cases, she discovers an unsolved murder is connected to a rare prehistoric fossil. Meanwhile, Sherlock finds himself in uncharted territory when his duties as a sobriety sponsor cross his personal boundaries.

Neal and Peter race against a criminal mastermind to unearth an invaluable treasure hidden in New York.

As Annie prepares the cafeteria for the midterm dance, she and professor Hickey must deal with the head custodian, the head of IT and the head of parking.

Arrow offers to train Roy so he can learn to control his newfound super-strength. However, Roy is a rebellious student and refuses to listen unless Arrow reveals his true identity, which Oliver refuses to do. Meanwhile, the Bronze Tiger escapes from prison and steals Malcolm’s earthquake machine to sell to the highest bidder. Oliver, Diggle and Felicity attempt to stop the transfer, but Roy gets in the way, putting everyone in danger. Laurel is disbarred and spirals out of control. Moira is thrilled when Walter asks her to dinner, but his reason surprises her. Thea encourages her mother to ask Walter to reconcile.

Monroe leads Connor and Charlie on a risky mission, as Miles and Rachel keep an eye on things in Willoughby. Meanwhile, Neville gets a new assignment and Aaron reunites with an old friend.

On the 200th episode, The Mother recounts how she met Ted and what she’s been up to for the past eight years.

Riley and Gabriel go on a covert mission in Syria in order to rescue American journalists being held hostage; the truth about Riley’s past with her ex-boyfriend is revealed when they are forced to work together.