Final answer:
The infinitive phrase 'to overthrow Queen Elizabeth I in 1586' functions as an adjective in the sentence.
Explanation:
In the sentence, 'Mary Stuart, Queen of Scots, was caught plotting to overthrow Queen Elizabeth I in 1586,' the infinitive phrase 'to overthrow Queen Elizabeth I in 1586' acts as an adjective. It describes the action that Mary Stuart was caught plotting.
Learn more about role of infinitive phrases in sentences here:
https://brainly.com/question/1627408
