The conflict was instigated by Bakuda (colaborating with Uber and Leet) kidnapping Bitch. When the Undersiders tried to rescue her, they were attacked.
With the Undersiders escaping Bakuda's custody they head to Doctor Q's to get medical attention for their wounded members. Further they are forced to contact Skitter's father to get them medical attention.
Immediately following the battle, Bakuda began her bombing rampage throughout Brockton Bay. And successfully breaks out Lung.