Defiant is the first story arc of New Warriors vol. 4, running from issues 1-6. It deals with the reemergence of the underground superhero team New Warriors in the public eye. The former team had been infamously immortalized as the "baby killers" of Stamford, Connecticut, where a mismatched pursuit led to the death of many innocent civilians and all but one of the team's members as well.
This incarnation of the New Warriors are active protesters of the Superhuman Registration Act (SHRA) and the man who is spearheading the campaign, Tony Stark. The team, made up of mutants who were depowered on M-Day, are a mystery to the public at large as well as to each other. This arc unravels the identity of Night Thrasher, who was believed to be killed in the Stamford tragedy as well as the new identities of some notable former mutants, including former X-Men Jubilee (now going by Wondra) and Chamber (now known as Decibel).
The group also tries to recruit former New X-Man Sofia Mantega (formerly known as Wind Dancer), though their attempts are unsuccessful as the very cautious teen is weary of committing to a new family after being tore from her former life after the events of M-Day.
When the group encounters the Zodiac, an inadequately trained member falls prey to inexperience. While the team is down and out, Sofia Mantega offers a distraction for the group to gain an upperhand and to save a young boy caught in the crossfire. However, she is shot from behind by one of the Zodiac's members and is severely injured.
As the team begins to dismantle due to their failures, Sofia reemerges from her recovery to bring the group together for a chance at solidarity and companionship.