This film begins in the 1970s, with the arrest of a Catholic priest named Fr. Geoghan, who has been caught molesting a child. The assistant D.A. and another priest convince the family of the boy who has been molested to let it go. The charge is then dropped from the priest's record, signaling to audiences the power of the Catholic church.
Then, the film flash-forwards nearly 30 years to 2001, when the Boston Globe hires a new editor named Marty Baron. Baron encourages the so-called "Spotlight" team of investigators/reporters to pursue a story which would announce the Catholic church's widespread systemic abuses, and subsequent cover-up of children.
Initially, the "Spotlight" team finds that only one or two priests had abused kids thanks to the help of a lawyer, Mitchell Garabedian. However, they quickly discover that dozens of priests (someone tells the team that 6% of priests are molesters, a figure which they find to be essentially correct) had abused hundreds, if not thousands, of children. They also found that church's leadership (specifically, the Pope and Cardinal Bernard Law) played a large role in covering up of the abuse.
The team is interrupted in their research by the gruesome and horrific 9/11 attacks but they eventually carry on, putting out a story which dramatically changes the Catholic church; and even the world.