After arguing with Sheldon, Howard tries to make amends by taking him to NASA headquarters in Houston. Penny has second thoughts about quitting her waitressing job when her car dies. Amy gets involved in trying to find Raj a date.
After an anonymous complaint is issued by one of their own, the hospital implements a non-fraternizing policy causing the couples to panic. Meanwhile, Emma and Owen talk about the future, Cristina and Meredith enjoy a little girl time, and Richard enlists the residents to help research a rare cancer case.
Nadia recalls her centuries-long search for her mother. Stefan, Caroline and Matt come up with a desperate plan to save Elena's life. Damon baits Tyler into an ugly confrontation and seeks revenge against Dr. Wes. Bonnie learns a terrifying secret that threatens the lives of all her friends.
The British Foreign Office, led by foreign secretary Sir Edward Grey, receives news of an assassination in the Balkans. In Berlin, the kaiser thinks he can exploit it for his own advantage.
Determined to cover up the truth by any means necessary, Harold's sworn duty to protect and serve suffers in the aftermath of the accident.
A lightning strike at a church picnic gets the guys to start thinking about how there’s no justice in sickness and injury, because like it or not, the “rain falls equally on the just and the unjust.” After a discussion of karma, the guys volunteer to teach CPR to disadvantaged kids only to later be given killer Bears tickets for the same day they’re supposed to teach.
Janet is overwhelmed with guilt about Blakely's death, and Det. Campbell believes his demise could have something to do with an old case; Erin and Owen are preoccupied with a bikie murder.
Walden thinks his girlfriend is cheating on him; Alan starts dating Larry's sister, Gretchen (Kimberly Williams-Paisley).
Harry, Michelle and Zoey dole out conflicting love advice to Billy, while Harry tries to deal with his newly discovered crush on Rose. Meanwhile, Rose can't wait to start dating a cute father at her baby's play group, but she’s not happy when she finds Harry spying on her date. Jonathan is thrilled to come to Harry's rescue, since Janet and Anastasia aren't interested in his advice.
Holmes and Watson consult on a case in which a man suspected of murdering his wife years ago receives a ransom demand for her safe return. Meanwhile, Lestrade overstays his welcome at the brownstone and seems unwilling to leave.
Mary must decide whether to marry Bash or Francis, who returns accompanied by Lola. Meanwhile, Mary's mother visits and pushes her own agenda, and her mere presence in the castle troubles both Henry and Catherine.
Voight's son may be involved with the Fitori murder case, intensifying tension between Antonio and Voight; Ruzek helps Burgess get retribution.
Liv steps out of her comfort zone when she meets charming Brit, Ron. Jessica and Fab compete over the handsome bartender while Tom learns how to be a wingman.
Tony Warner's performance as Macbeth is the toast of London's West End. It would be very bad luck indeed if he was suddenly indisposed in some way. Except for Jim, his ever-hopeful understudy, of course.
Following the violent attack she suffered in prison, Lindsay is granted special dispensation to visit her dying mother. Meanwhile, deputy chief constable Dryden shrugs off allegations about his relationship with Lindsay and possible links to the ambush.
Ben tries to score a second date with Heather in order to win a wager with Riley. Elsewhere, Bonnie asks Danny to end her relationship with Brad for her, and then she becomes interested in Brad's dad; and Tucker uses Emma to improve his dating life.
One of Billy's friends with muscular dystrophy dies forcing the realization on the guys that Billy doesn't have much time left. Jim copes by chasing after the dead guy's sister.
Brick makes it hard for Mike to relax during the vacation he was forced to take; Frankie is furious when she learns that Axl was in town without letting her know; Sue tries extra hard to please her customers after receiving a bad review.
As Philip investigates the fallout from the last operation, Elizabeth sticks close to home, concerned for her family until she gets a mysterious distress signal. Meanwhile, a walk-in arrives at the Rezidentura - providing both Nina and Stan with unique opportunities.