18.2.1792 Road to Ruin. (te0119) by Thomas Holcroft. Also relevant to this text are 25.3.1792 Mercier's Road to Ruin (already tagged to te0119) / 3.4.1792 'talk with Holcroft of literary monopoly' / 8.4.1792 'Holcroft calls, talk of literary monopoly. Dine at Holcroft's, his explanation with Mercier; sup with him at Fenwick's, explanation' / 6.8.1792 'Smith in the Road to Ruin' when Thomas Cooper appeared in that role at Newcastle / 4.11.1792 Mercier adv at Holcroft's; talk of languages and precision
I would suggest that the Mercier on 8.4.1792 and 4.11.1792 was the playwright Louis not his brother Charles Andre as coded in the GD website, though the latter is supposed to have collaborated with Louis on some of his works. The next Mercier entry on 12.11.1792 specified C Mercier. It looks like the charge of plagiarism was made by Mercier against Holcroft, though it could be the other way round. You'd have to know the plays of both to make an educated guess.