The team tries to relax during a mandatory day off, until an explosion leaves three people dead — and reveals that one scientist is a walking time bomb.

When a terrorist attack decimates a Jaffa summit Teal’c strikes out on a quest for revenge, believing that the perpetrator is one of his own pupils.

Can Sylar be stopped? Will Linderman’s vision live on with Nathan? What will it take for Peter to save the world, what sacrifices will be made? With all the horrible predictions unfolding before them the heroes face moments of pain and peril in Kirby Plaza.

CTU discovers where Philip is hiding and Daniels orders an air strike in a desperate move to appease the Russians. Jack and Bill go after Josh alone before the bombers find their target.Lennox persuades Daniels to grant leniency for Bill and Karen. In the wake of the close call, Daniels begins to question his choices as acting president.Chloe gives Morris some surprising news that alters their relationship, while Marilyn is reunited with Josh at CTU.

Doyle takes Josh to meet Phillip in the hopes of retrieving the circuit board, but his conscience bothers him over the exchange.Karen puts her career on the line when she uses Bill to help break Jack from custody. Jack and Bill track Phillip, but not before he pulls a fast move that reaps serious injury to Doyle.Nadia has a conversation with Milo’s brother, while Chloe suffers from a mysterious medical problem that strikes her at the wrong moment.

The team discovers the last of a civilization in suspended animation, whose survival is at risk when their station is critically damaged.

SG-1 realizes they have stepped through the gate into another planet’s museum — but are mistaken for a band of zealous rebels who have taken hostages.

Angela Petrelli is forced to play a bigger role in Nathan, Peter, and Claire’s life. The truth about the death of Nathan and Peter’s father is finally revealed along with his true identity. When Nathan finds out that he may have a chance to become more than a Congressman, he is confronted with a decision that he must make. As election day nears some try to leave NYC. HRG and Matt learn another surprising secret. Also, Sylar is eating another hero’s brain. Hiro’s dad returns.

It’s still Marshall and Lily’s big wedding day but now we’re at the reception. Robin tries to tell a story but keeps getting interrupted. Barney tries his hardest to figure out Ted and Robin’s secret.

Jack runs a desperate tactic to free the CTU hostages from their captors. He manages to intercept Cheng, who plans to deliver Josh to his grandfather in exchange for the circuit board. Jack is forced to allow Cheng to escape in order to save Josh’s life.Lennox continues to monitor Lisa as she plants evidence for Mark to deliver to the Russians. The situation takes a nasty turn when all does not go according to plan. Meanwhile, Daniels tries to run a bluff on the Russian president, but finds he’s playing a bad hand.Nadia finds herself facing a hostile investigation over the security breach, while a decision from Daniels pits Doyle against Jack.