Every season of Zero Day ever, ranked from best to worst by thousands of votes from fans of the show. The best seasons of Zero Day!

Former President George Mullen's comfortable retirement is upended after he's asked to lead an investigation into a horrific cyberattack.

Episode 1

Mullen's commission investigates a hacking ring. President Mitchell weighs retaliation. A powerful figure has demands for Roger.

Episode 2

Mullen's initial arrests draw blowback from the public — especially TV pundit Evan Green. Alex faces pressure to investigate her father.

A shock to the financial system increases scrutiny on Mullen's commission. Valerie investigates Proteus. Roger must make a difficult choice.

A personal tragedy reopens old wounds for the Mullen family. Speaker Dreyer pushes for a change in leadership. Sheila testifies before Congress.

A new threat creates further unrest across the nation. As he narrows in on the culprit, Mullen is faced with an agonizing decision.

A former U.S. President is called out of retirement to find the source of a deadly cyberattack, only to discover a vast web of lies and conspiracies.