Detective Comics #38

Batman

My, this is a red letter day. Just look at the cover of this comic! This issue introduces an absolute pillar of Batman's cast of characters: Robin. I'll let the comic speak for itself, here:

Introducing in this issue an exciting new figure whose incredible gymnastic and athletic feats will astound you . . . a laughing, fighting, young dare devil who scoffs at danger like the legendary Robin Hood whose name and spirit he has adopted . . .
Robin
The Boy Wonder

Here we see the familiar story of the Flying Graysons--father, mother, and young son Dick--an acrobatic act in the Haly Circus. The owner, Haly, refuses to pay protection money, and the next night the ropes on the trapeze have been cut, and both the elder Graysons fall to their deaths. Dick learns that the racketeers are responsible for his parents' deaths, and intends to report them to the police, when he is approached by the Batman. Batman tells Dick that he can't go to the police: "Because this whole town is run by 'Boss' Zucco. If you told what you knew you'd be dead in an hour." Batman reveals to Dick that his parents, too, were killed by a criminal, which is why he's dedicated his life to fighting crime. Dick pleads with Batman to let him join him, and Batman eventually agrees, teaching Dick what he needs to know to be a masked crime fighter: Robin, the Boy Wonder.

After months of practice, it is finally time to put these skills to use. Dick goes undercover, disguised as a newsboy, in order to track down the racketeers that work for Zucco. Then, Batman goes about, foiling the racketeers' attempts to extort money from the local businessmen, and sending his regards to Zucco. Batman's interference and taunting lead Zucco to see to the next job personally. Batman and Rob use this opportunity to stop the men while gathering evidence to put away Zucco.

With Zucco taken care of and Dick's parents avenged, Bruce asks what he plans to do--whether he plans to go back to the circus. Dick replies: "No I think Mother and Dad would like me to go on fighting crime. As as for me--well . . . I love adventure!". So begin the adventures of Batman & Robin.