Dr. Lucy Bauer was a scientist obsessed with the mystical Darkhold. She became trapped dimensions (or became a ghost) after being forced to be a test subject for Dr. Elias Morrow's experiment.
Lucy became determined to regain her physical form and killed anyone who got in her way.
Lucy was killed by the Ghost Rider.
Dr. Lucy Bauer and her husband Dr. Joseph Bauer spent years searching for the Darkhold all over the world and they eventually found it. When they both read the book, it showed them how to build a quantum particle generator, a machine that channels extra dimensional energy and converts it into new matter.
Lucy and Joe then founded Momentum Alternative Energy Labs and recruited a team of other scientists, including Elias Morrow, to help them with their project.
When they built their first prototype generator, the experiment was a success and they were able to create a brick of pure carbon. There idea was they could use the generator to create rice, wheat, and other foodstuff to end world hunger, but Joe, later, changed the goal of their project and wanted the power to generate matter himself.
However, after Elias learned about Joe's true ambitions, Elias wanted the power for himself. Elias used Lucy and the other scientist as test subjects for his experiment; he forced them into a full-scale generator and activated the machine which caused each of them to become stuck between dimensions (or turn into "ghosts").
Somehow Lucy and the others became trapped inside the power cells Elias used to power the generator.
In "The Ghost," while in prison, Elias tells the Chinatown Crew that there's a some kind of powerful weapon inside the power cells at Momentum. The Chinese hire four members of the Arian Brotherhood to steal one of the cells and then deliver it to a warehouse.
After the cell is delivered, with Lucy trapped inside, two of gangsters open the box to see what's inside and become infected with the "ghost virus." They then begin hallucinating and start killing each other prompting the other gangsters to shoot them.
Later, they deliver the cell to their boss who opens it thereby releasing Lucy and causing everyone in the room to become infected. The criminals start fighting with each other and Lucy leaves.
At the end of the episode, it's revealed May was also infected by Lucy.
In "Meet the New Boss," at the beginning of the episode, Lucy goes to her old home look for her husband, but is surprised and confused when she finds someone else living there. The man living at the house says his family has been living there for years. Lucy leaves, but not before infecting the man.
Lucy goes back to Momentum and releases the other ghosts from the power cells. Lucy explains to them how they're gonna find Joe and the Darkhold then they're gonna kill Elias and find a way to turn themselves back to normal.
In "Let Me Stand Next to Your Fire," Lucy learns Elias beat Joe into a coma and he's being lying in a hospital bed for years. Lucy goes to the hospital and reaches inside Joe's head to wake him from his coma. Lucy then forces Joe to tell her where the Darkhold is and he tells her, after Elias' experiment, he buried the book where he and Lucy found it.
In "Lockup," Lucy unearths the Darkhold only to learn that in her current ghostly form the pages of the book remain blank to her.
Later, Coulson and May go to the prison where Elias is, thinking Elias could tell them more about the Darkhold and what Lucy is after, but they quickly realize Lucy and the other ghosts are already in the prison and have infected all the guards and the warden with the ghost virus thus driving them all crazy and causing them to attack Coulson and May.
When Lucy learns S.H.I.E.L.D. is in the prison, she tries to kill them by releasing every prisoner from their cells.
Lucy breaks out Elias and forces him to come with her; however, it can be inferred, that Elias wanted to go with Lucy because Mack told him that Lucy had the Darkhold. Lucy takes Elias to Momentum, kills the S.H.I.E.L.D. agents guarding the facility by infecting them with the ghost virus, and then explains to Elias she wants him to read the book for her and use it to fix her.
In "The Good Samaritan," Lucy wants to repeat the original experiment, only this time with more power to the machine, in order to return her to normal. However, S.H.I.E.L.D. arrives to rescue Elias and Lucy is killed by the Ghost Rider.
Elias' experiment caused Lucy to become trapped between dimensions (or turned her into a ghost) which gave her powers:
- Intangibility: Lucy, for the most part, couldn't physically interact with the world. She could walk through walls and objects like bullets passed right through her.
- Ghost Virus: So named by Dr. Radlciffe, anyone that Lucy touched became infected with the virus and began having hallucinations which drove them violently insane. Eventually the virus causes the death of its victim; Simmons described it as the virus scaring its victims to death. Radcliffe and Simmons created a cure for the virus.
- Ghost Rider was the only one who could kill Lucy and he was immune to the virus.