As Joe Rorchek investigates a series of arson fires that occupy his firefighter sons, their unit also copes with the introduction of their first female crew member.
The battalion intends to give a boy a citation for his help with fires. But those plans are on hold when it's discovered the lad is the one who has been setting the blazes.
Joe gives away bride Constance to firefighter Charlie Bowers. The newlyweds' world is shattered when Charlie is fatally injured. Ted, the best man, takes Charlie's death very badly and freezes during a subsequent incident.
Danny learns that a young woman in his class is having dreams about some recent fires with details very accurate. The situation takes a twist when the visions start featuring Danny.
Danny finds out that his old gang is being framed for arson by their rivals. While trying to help Danny finds himself trapped in a blaze with members of the group responsible for the fires.
After a religious family's rented home burns down by accident, their adopted son convinces himself that it was arson and seeks revenge against the innocent landlord.
The Rorcheck family finds themselves at odds with fellow firefighters when they befriend a crippled former colleague. The problem is he blames Ted that injured him.
A pyromaniac arsonist is committing a series of firebombings with the crew of LAFD Station 1, especially Firefighter Haley Green, singled out in threatening letters.
An old mining site that has filled up with toxic waste is hidden from view. When it suddenly collapses Joe, Haley and Danny are trapped and their lives in danger. The crew struggles to rescue them.