Before the start of the novel, Lydgate works and studies in France. He falls in love with an actress who murders her husband and makes it look like an accident. She says it's because she was "tired" of him.
Lydgate is disillusioned and leaves France.
He decides to settle in Middlemarch, where he'll help start a new Fever Hospital in which he'll be able to test out all his new theories.
One of his earliest patients is Fred Vincy.
He's at the Vincys' house so often that he ends up falling in love with Fred's sister, Rosamond.
Even though he doesn't have a lot of cash to support a wife, Lydgate decides to get married, anyway.
He has faith in himself and his capabilities, and is sure that he'll be able to pay the debts later.
All the other doctors in Middlemarch are set against him, and he has a hard time making ends meet.
Debts pile up.
Rosamond stops listening to him, and just does her own thing.
He gets depressed.
When he's ready to throw in the towel, auction off the house, and move to London, Mr. Bulstrode offers him a fat loan.
The next day, a patient he'd been seeing dies under Mr. Bulstrode's care.
A scandalous rumor goes around that Bulstrode had bribed him to help kill that patient.
Now Lydgate really needs to leave town, because no one will believe his side of the story.
No one except Dorothea! Dorothea supports him, gives him a loan so that he can give Bulstrode back the money, and encourages him to stay in Middlemarch.
Lydgate ends up leaving eventually, anyway.
He never completes his life's ambition, and dies feeling like a failure after the close of the novel.