Otto Heckel (オットー・ヘッケル, Ottō Hekkeru) is a professional burglar who bumped into Dr. Tenma while thieving in congressman Springer's home. Heckel, although very much preoccupied with money, proved to be a very useful person to Tenma, all because of his talent in finding substantial information on practically anyone, even getting so far as to breaking into police stations to access classified information.
Heckel first encounters Tenma during Heckel's breaking in to the Springer's residence. That place has been empty for a month then, after the Spinger's has been killed by the Junkers' group. Heckel tried his luck on this lavish estate and was not disappointed by what he has seen: the placed was untouched and the valuables are still inside. However, when he was about to enter Congressman Springer's study, he felt a chill run down his spine. He dismissed the feeling as unnecessary and continued to opening the study to find the wall safe. Tenma then appears with a gun pointed at Heckel's head. At first he thought Tenma thought was a burglar like him and tried to work things out amicably. But then Tenma tells him he is not one of their sort. Police sirens were suddenly heard and they both fled the Springer residence. He attributed this bad luck to the missing cherry in his Manhattan that morning.
Heckel and Tenma went to an alley for refuge, and Heckel recognized Tenma as the doctor who was involved in the murder of the Springers. At first Heckel did not want any connections with him, but as his instinct for money kicked in, he offered Tenma a job in the underground as a mobile doctor. Tenma did not like the idea and left Heckel. Heckel, not wanting a large sum go away that simply, tried to buy Tenma's attention by telling him he knew who the killer was. Tenma then asked him if he resembled Johan, but Heckel knew him not. Heckel promised him information about the perpetrator if in turn Tenma would work for him. Heckel pointed out to Tenma that the killer lived in the third floor of an apartment building not far from the Springer residence. Heckel knew the guy because he showed up when Heckel was about to hit the Springer residence, peeking in. He also offered to stand as witness for Tenma and clear his name in exchange for a 'yes' to his business proposal.
Tenma heard none of it and decided to confront the man int he third floor. Heckel was hesitant to follow him, but Tenma could be his money-maker and opted to following him inside.
Heckel then rushed inside and shouted to know if Tenma was still alive. When he entered the room, he warned Tenma that guy has gun, but Tenma ignored it. The guy then started to tell things about his mother and how they would take a stroll around sunflower fields during summer days such that. When Tenma interrogated him if someone asked him to use his gun, he said he talked to a man in a bar one day. He described this man as one with a beautiful smile and goes by the name Erich Springer. They met so many times that they soon became friends and Erich invited him to come over his home, the Springer residence. He told Tenma that Erich had been living with the Springers as their son for about a year now, but Heckel tells Tenma that he had never seen the man the guy was describing.
The guy then divulged Congressman Springer's cheating and his removal of his sunflower bed in his garden to make room for more parking space. He admitted that they were a nice family overall, but Erich feeling of not belonging to the family and his eventual split with the Springers contributed to his hate to that family. Erich then asked him to eliminate that family for him, because for them, mistresses are a most disgusting thing. It also hit the guy because his own mother was another man's mistress.
Heckel, not letting the opportunity of inside information go, asked him if he happens to know where the wall safe is located. He told Heckel that it can be found on the second floor, at the back of the study. Heckel was delighted by the candid and instant answer that he decided to leave at once, advising Tenma to leave at once too. After the guy told Tenma a few more sentiments, he asked him to leave. However, the guy recalled who Tenma was, and told him the Erich left a message for him in the study. After that, the guy pointed the gun in head and shot himself dead.
In the study
Heckel and Tenma visited Congressman Springer's study. Heckel pried open the safe and emptied the vault. Meanwhile, Tenma looks around for signs of the message Johan left for him. Heckel again convinces Tenma to drop his quest on finding Johan and work with him. Tenma then notices a painting of an eighteenth century woman, and took it off the wall. He shone his flashlight on that part of the wall and saw the message. Heckel commented on Tenma's shaking.
Otto Heckel, in the English dub, resembles the character Bugs Bunny in speech, voice, attitude, and looks (with his front "rabbit" tooth. It is almost uncanny hearing Heckel say "doc" in a sentence, akin to Bugs Bunny's "What's up, Doc?".