The story begins with Robert the Bruce, along with other prominent Scottish nobles, meeting with Edward I to accept him as their king in around 1306. They had already led a rebellion that was unsuccessful, where Edward I, Hammer of the Scots, had earned his nickname by winning against the Scots. Robert still wants to be king, as his family has ancient lineage to the thrown of Scotland, but other claimants exist for the Scottish throne and none of them are in position to attack the English due to their strength and possession of many key areas of Scotland. John Comyn was another Scottish noble who also had perhaps just an equal or maybe stronger claim to the Scottish throne.
William Wallace is the last major Scottish figure not to accept Edward I as king. Eventually, after several years of being on the run and hiding in the highlands and other regions, William is killed. This is shown in the movie as inspiring rebellion against the English, that the death of Wallace somehow triggers a nationalist rage that sparks Robert to begin to plot to take back Scotland. As the Bruce begins to plot the rebellion, he meets with Comyn in Greyfriars church. However, the two quickly make their own claims to the throne of Scotland and Comyn does not show willingness to side with the Bruce against Edward I. This leads to Robert the Bruce striking and
killing Comyn in the church's high alter , which is consider sacrilegious and may have kept some of the Scottish nobles from siding with the Bruce as the rebellion begins.