What is the main conflict in Elizabeth the Great by Elizabeth Jenkins?

Throughout her reign, Elizabeth was threatened by various plots to murder her and place the Catholic Mary Queen of Scots on the English throne. A number of conspiracies against her life and crown were uncovered, resulting in many executions for treason, including the execution of Mary Queen of Scots in 1587. However, upon Elizabeth's death, King James VI of Scotland, the son of Mary Queen of Scots, was named as her successor, making him King James I of England.