Nineteen year old Dorothea Brooke is determined to lead a worthwhile life and to help others. When she meets the middle-aged scholar, Mr Casaubon, she believes marriage to him will provide her with the useful role for which she longs. Meanwhile in Middlemarch Dr Lydgate, bent on medical reform, is distracted into romance with the alluring but superficial Rosamond Vincy.

Both Dorothea and Lydgate, disillusioned with their marriages, find their idealism frustrated: and for Dorothea, her husband's enigmatic but fascinating nephew, Will, is an added complication.