On 10 December 1684, a true bill of manslaughter was brought in against him for causing the death of Sir James Halkett during a fracas at a theatre; but he escaped punishment.
In May 1692, he was mentioned in a proclamation as a dangerous Jacobite, but he soon felt it safe to return to his old haunts, and in June 1695, he was temporarily taken into custody for rioting in a Drury Lane tavern and drinking King James's health.
After the death of Queen Mary, Porter associated himself more closely with Sir George Barclay, Robert Charnock, and other conspirators in the Jacobite plot.
On the eve of the intended assassination, 21 February 1696, the conspirators assembled in the lodging that Porter shared with Charnock in Norfolk Street, Strand.
In November 1696 Sir John Fenwick was alarmed at the information possessed by Porter on the ramifications of this and previous plots, and he made a strenuous effort to get him out of the country.