After the sudden death of his father, Nicholas Nickleby, a young and kind-hearted gentleman, is left to support his mother and sister. The family, now poor, seeks help from their cold and greedy uncle, Ralph Nickleby, who cares only about wealth and power.
 
Nicholas is sent to work as a teacher at Dotheboys Hall, a brutal and abusive boarding school run by the cruel Wackford Squeers. Horrified by the mistreatment of the children—especially a boy named Smike—Nicholas stands up to Squeers and escapes the school, taking Smike with him.
Back in London, Nicholas struggles to find honest work, facing setbacks and dangers, but always acts with integrity. Along the way, he:
Joins a traveling theatre troupe led by the comic Mr. Crummles,
Protects his sister Kate from predatory men connected to their uncle,
Helps those in need, including the suffering Madeline Bray, with whom he falls in love.
Meanwhile, Ralph Nickleby tries to sabotage Nicholas at every turn, using deceit and manipulation. But in the end, Ralph's cruelty leads to his own downfall, while Nicholas's kindness and loyalty are rewarded.