The turning point in his career came in 1683 when Melville and his son David Leslie-Melville, the Earl of Leven, were accused of complicity in the Rye House Plot.

a Whig conspiracy to assassinate King Charles II and his brother the Duke of York (the future James VII).

[1] To escape arrest Melville, together with his son, fled to the Netherlands where they joined the band of British Protestant exiles at the court of Prince William of Orange.

After the "Glorious Revolution" of 1688 Melville played a prominent part in Scots and English politics, most notably in the Convention Parliament which offered the crown of Scotland to William of Orange and his wife, Mary, daughter of the deposed James VII.

Later Morton is forced to flee to the Netherlands where (living under his mother's name of Melville) he becomes one of William of Orange's supporters, before returning to Britain in the wake of the Glorious Revolution.