I've heard so much about you. You're even more disappointing in person: so weak, so pathetic...
Dr. Henry Jekyll is a supporting character on Once Upon a Time. A kind and intelligent man with clearly more than a few inner demons, the doctor formulated a serum to separate his good half from his bad one; of course, it only worked some of the way, causing him to flit endlessly between himself and the villainous Mr. Hyde. Eventually though, the two of them separated and a certain group of heroes were kind enough to bring Jekyll home with them to the town of Storybrooke, but it seems his capacity for evil wasn't quite absolved, and he ended up dying while committing villainous deeds of his own.
Before the Curse
Although separate from his dark half, Jekyll grows enraged enough to kill. ("Strange Case")
Henry Jekyll, upon becoming a doctor, spends years trying to help his patients by developing a serum that should be able to split a man's personality into two halves - good and evil. During these years, he is also pining after the daughter of a fellow doctor: Mary Lydgate. She eventually arranges a meeting for him and her father, Dr. Lydgate, but he refuses to back Jekyll's work by giving him academy membership because he deems it too "dangerous". Jekyll is then approached by Rumplestiltskin, who has interest in the serum and uses his magic to complete it, then convincing Jekyll to test it out to see if he can't get that academy membership after all. As Mr. Hyde - his other half's name - he is successful in intimidating Lydgate into handing over an academy pin, and Jekyll is ecstatic that his serum actually works. However, Rumple points out that one success proves nothing, but two would be hard to deny, and so he convinces Jekyll to drink the serum again so that he can use Hyde to seduce Mary on his behalf. Unfortunately, this goes awry when Mary ends up sleeping with Hyde instead, and when he wakes up the next morning, as Jekyll, he is utterly enraged. He ends up killing Mary in a struggle by pushing her from a window, then quickly framing it on Hyde by downing the serum. A witch hunt is instigated across London, and an angry Rumplestiltskin, who now sees the serum as a failure since Hyde had the capacity for love, banishes the doctor and his other half to the Land of Untold Stories where they'll be condemned to spend the rest of their days bound together. ("Strange Case")
After the Third Curse
You've met the warden. Trust me, I want to get away from him as much as you do.
The doctor repairs the Apprentice's wand. ("Only You")
When Snow White, Prince Charming, Captain Hook and Zelena are all accidentally sucked into a portal to the Land of Untold Stories, they come across Dr. Jekyll while he's trimming flowers from a garland in the garden of Hyde's mansion, and they have no inkling that he's a doctor as opposed to a groundsman. They need magic to get home but he is reluctant to talk to them in fear that Poole will punish him; indeed, Poole shows up and stuns the four heroes, proceeding to lock them all up in a cage. After Hyde has his fun intimidating them, Jekyll returns with the intention of helping them... on the condition that, when they return to the town of Storybrooke where they came from, he gets to come with them. They agree to his terms and end up giving him the Apprentice's wand, which broke as they came through the portal it created. He takes it to the laboratory to repair it, not being able to bring the necessary potions to the prisoners because Hyde would know they were missing, but once he's successfully fixed the magical artifact he is ambushed by Poole and forced to transform into his worse half. Hyde decides that Storybrooke is going to be his new home and he uses the wand to kidnap Belle, Rumplestiltskin's wife, so as to have the leverage he needs to carry out his plan. ("Only You")
Jekyll finally becomes free of Hyde. ("An Untold Story")
Jekyll wakes up in a straitjacket and uses a surgical knife to escape, taking the keys from a passed out Poole as he does so, he so that he may free the prisoners. He leads them out of the mansion and into the Land of Untold Stories, which they marvel at; they proceed to arrive at the doctor's apartment where he uses the flowers he was earlier trimming to complete the serum that's meant to separate one's good half from their bad half. He says that they can use it to defeat the warden, but then Poole shows up and forces him to transform into his worse self, leading the heroes to realize what story they're from. They flee while Hyde uses the completed serum to make it so that he and Jekyll become separate beings. He then attempts to strangle the doctor to death, but the heroes return and save him. Snow stuns Hyde and gives them all enough time to escape, but the warden soon finds them when they reach a dead end. It's then that pennies - or rather, wishes - start to fall from the sky and a portal opens to New York; Jekyll, Snow, David, Hook and Zelena all jump down it while Hyde misses his chance. Jekyll doesn't know how to thank the heroes for helping him get away, but they find a way for him to do so - by giving the last dose of his serum to Regina so that she can finally destroy her worst self, the Evil Queen. Of course, this doesn't work, and while Jekyll is being given the tour of Storybrooke upon everyone's return there, not only does the Queen rise again in New York, but Hyde shows up claiming that he now owns the town after a deal with the Dark One. ("An Untold Story")
Regina uses Jekyll to apprehend Hyde. ("The Savior")
Jekyll is among the townspeople present when the dirigible from the Land of Untold Stories flies through Storybrooke, delivering Hyde's "friends". After Emma and Regina fail to defeat this new villain, Jekyll helps search the blimp, and notes that what Hyde's reasoning for being in Storybrooke all depends on the people he brought with him, who have all fled into the woods. However, he offers to use the remains of the dirigible to make a weapon similar to Poole's, as it's the only magic that can control Hyde. He also constructs a pair of handcuffs that can go on Hyde once he's been taken down. As part of a ruse to get Hyde out of the mayoral office, which he has now taken over, Regina and the others arrive, with the former manhandling Jekyll. She offers to hand him over to Hyde if he agrees to vacate the office, but Hyde is more determined to keep things going his way. He tries to choke Regina, but Emma uses the weapon Jekyll made and blasts him, giving David and Hook enough time to formally arrest him. ("The Savior")
Two brilliant minds start to collaborate. ("The Other Shoe")
When bribing Mr. Hyde proves to be fruitless in finding out how the Evil Queen managed to survive getting her heart crushed, Regina and the Charmings turn to Jekyll instead, who thinks he might be able to find the answer by replicating the serum that created the Queen in the first place. Unfortunately, he can't get very far with just the equipment salvaged from the dirigible, and needs a proper lab if he's going to be able to accomplish such a feat. This frustrates Regina, but Snow soon has an idea as to how they can help the doctor with his task. She proceeds to take Jekyll and Regina to the garage of Dr. Whale, who is better known as Frankenstein. He has all the proper apparatus set up, and Jekyll finds it an honor to meet him, then beginning to collaborate on replicating that serum. As she watches them at work, Snow has the brilliant idea to move all the lab equipment over to the school once it's no longer in use and put the two doctors to work teaching, all as a part of her plan to get this town back to normal. ("The Other Shoe")
Jekyll's lingering capacity for evil is his downfall, and Hyde's. ("Strange Case")
Word soon gets out that Hyde escaped his cell and is now on the prowl with the Evil Queen when Jekyll discovers Mary's cameo necklace in his room at Granny's Bed & Breakfast, so he and Regina hightail it over to Emma's house to warn she and the other heroes of this matter. It is pointed out that Jekyll should still be working on replicating the serum in order to destroy them both, and so they return to the lab where it's recalled that Rumple was the one to help him complete it the first time. As such, while Emma and David go out searching for Hyde and the Queen, Regina goes to find Gold for his help, but this leaves Jekyll defenseless when the two villains show up at the lab - thanks to a beckoning spell the Queen placed on Mary's necklace. Hyde then trashes the lab, but Jekyll manages to save a small vial of serum, to Regina's joy when she turns up with Gold. When she wants Rumple to magic it to completion, however, he responds by ripping Jekyll's heart out, threatening to crush it if Regina does not pour the serum over his dagger so that he can use it on just Hyde - after all, he and the Queen have a deal. After regaining his heart, Jekyll heads on over to the Jolly Roger where Gold has trapped Belle, so as to keep her safe from Hyde. He brings an electronic baton with him and attempts to kill the poor, pregnant beauty, having decided that now is the time to claim vengeance for Mary. However, while he is attacking her, Hook comes to the rescue. A struggle ensues, and it ends in Jekyll being pushed into a spike protruding from the mast, impaling him. His death means that Hyde dies too, with the serum having failed since he had earlier switched the vials, and Rumple reclaims his stolen dagger. As Jekyll and Hyde's bodies are laid down together, the news sets in that the only way to kill a doppelganger is to kill the original - also, even when separated from one's dark half, the capacity for evil remains, just like it did in the "good" doctor. ("Strange Case")
Gallery of photographic stills released to promote the character.