Mad Dog Ladd is a former street thug in the town that Brandon Heat and Harry McDowell grew up in. Mad Dog has a weaker younger brother named Deed, who frequently got into fights with Brandon and Harry's gang before their deaths.
At some point prior to the start of the story, Mad Dog left the town he had grown up in for unknown reasons.
Harry speculates that Mad Dog had died, but in fact, Mad Dog had joined Lightning and returned as a member of the mafia. Angry at his younger brother Deed's weakness against Harry's gang and inability to fire a real gun to kill, especially as it also gives him a bad name, Mad Dog walks to Harry's hangout, but finding nobody there but Jolice, kills the cook with a single shot to the head. Harry, Brandon, Kenny, and Nathan later return to discover Jolice's corpse, and are forced into hiding as a result of Mad Dog's violence. Later, Mad Dog walks into a laboratory owned by Millennion and kills all the scientists there, sparing only Dr. Tokioka, who he kidnaps to work for Lightning.
Mad Dog later looks after his younger brother, hoping to see him kill his rival gang to make up for his earlier defeats. However, when Deed was following Brandon, he also runs into the far more experienced Jester, whose mastery with his own pistol scares Deed away. Mad Dog, who was watching from the nearby alleyway, kills Jester with a shot to the chest while again expressing shame at his younger brother's cowardice. When Harry, Kenny, and Nathan arrive, Mad Dog kills Kenny, and when Nathan holds him at gunpoint with Kenny's toy gun, kills him as well. Brandon is grazed with a shot to the shoulder and is unable to fight as Mad Dog prepares to kill them.
However, Mad Dog's kidnapping of Dr. Tokioka, who was a Millennion scientist, and recent killing of Jester, who was a veteran hitman for and friend of Big Daddy, attracts the attention of Bear Walken, who laments Jester's death and inquires about the notes that Mad Dog had stolen. Knowing that he is doomed to die having crossed Bear Walken's path, but wanting to choose where to die, Mad Dog gets into a gunfight with Bear, who manages to disarm him. Bear shoot him in the arm, interrogating him about Dr. Tokioka's notes. Mad Dog nonetheless refuses to tell and Bear throws his gun at Brandon and Harry so that they could avenge their friends. The boys hesitate and Mad Dog makes a final grab for the gun, only to be killed by one of Bear's derringers. Bear berates the two for being a "bunch of stupid brats".
Not long after, Harry and Brandon confront the deceased Mad Dog's younger brother Deed, Harry killing him with the gun that Bear lent them.