Tom Corbett Space Cadet #7

Jim, Tom Corbett's friend, discovers his own brother Bob Keen imprisoned on an asteroid, framed for a crime and serving time with a criminal gang. When Jim attempts to help his brother escape, Bob initially resists, fearing the consequences, but eventually agrees to break out. Tom and the other space cadets pursue Bob to the outlaw colony, where a confrontation occurs before Bob's innocence can be proven and he is freed from his unjust sentence.