Mr. Murdstone is David Copperfield's wicked stepfather. He marries David's mother when the boy is conveniently away at the coast. When David returns home, he's in for a nasty surprise, because his new stepdad is a cruel, sadistic bully. He regularly beats David for no good reason; he dominates and controls David's mother; and for good measure, he brings his equally disgusting relatives into the house, which they proceed to take over and treat as their own.
Murdstone provides David with what he fancifully regards as gainful employment in the family wine-bottling factory, "Murdstone & Grinby." Unfortunately, this isn't much of a career move, as David is forced to slave away in a menial job, treated little better than a slave. We get the impression that his evil stepdad sent him out to work just so that he could get him out of the way.
Life at the factory becomes so utterly wretched and unbearable that David is forced to run away and find refuge with his eccentric but lovable great-aunt, Miss Betsey Trotwood. When Murdstone discovers that David has gone AWOL from the factory, he sees an opportunity to remove him from his life altogether and arranges for Miss Betsey to become David's legal guardian, but not before Betsey gives him a richly-deserved tongue-lashing for his appalling treatment of the young lad and his family.