A car pulls away from a known drug house and won't stop for police in Corpus Christi; an undercover cop's work leads to the arrests of two pimps and a prostitute in Las Vegas; an officer in Tampa witnesses a driver make several traffic violations.

Gibby wants to sabotage Sam and Freddie's romance, and Carly is torn about whether to help him.

After Ratchet injects himself with untested synthetic energon, his behavior becomes erratic and threatens the Autobots safety.

A scandalous photo from Alex's phone is circulated on the campus while Harmon ponders how to respond to suggestive pictures that he accidentally received from Daniels and Debra in the Season 3 premiere. Sal Governale; Richard Christy.

The rivalry between Kate Leigh and Phil Jeffs reaches boiling point, leading to a legendary street battle between their rival gangs. Jeffs is determined to put Kate and Tilly out of business by poisoning their cocaine supply and slashing their workers. The police create Australia's first drug squad to fight the deadly cocaine epidemic, and Kate starts an affair with a sexy young gangster, angering her faithful lieutenant Wally.

The final set of hopefuls audition in front of the judges hoping to gain a place in the next round of the competition.

The team has been left shocked by Lucas's betrayal, and with Harry Pearce on gardening leave, Section D has a new leader called Erin Watts. She has brought Calum Reed with her into the team. Harry Pearce manages to win his MI5 employment tribunal and is soon back on the Grid in the thick of the action. Secrets end up being discovered after Max Witt, a retired spy and Harry's colleague in Berlin during the Cold War, is discovered to have been murdered.

The Great War is making life at Downton feeling unsettled. Isobel has some surprising news about Matthew which ends up rocking the family even more. Ethel, a new maid at Downtown, manages to get on the wrong side of O'Brien. Bates returns and gives Anna some news which will change her life.

Tim is having no luck tracking down Miranda and Shane since she dropped the bombshell that Shane is his son... until Shane - on his own - surprises everyone by just showing up at Heartland. And Mallory entertains the idea of going with the recently-single-again Jake to the Spring Fling. There is however - as you might expect with Mallory - a "but" attached.