A subplot is a secondary storyline or plot that occurs alongside the main story in a book, movie, or play. It often involves different characters or events that provide additional context or entertainment to the overall narrative. Full definition
The other half of the movie involves Cecil's home life, which is reduced to his wife Gloria (Oprah Winfrey) turning from a life of heavy drinking and carrying on an affair with a neighbor (Terrence Howard) to becoming a better person, and a contrived series of subplots involving his eldest son Louis (David Oyelowo), who sees his father as weak and wants to fight the good fight for equality. (markreviewsmovies.com)
Then there are the fan - vexing elements of his supposed half - human heritage and a strong romantic subplot with his companion Grace (a doctor who performs heart surgery right after going to the opera). (mutantreviewers.wordpress.com)