A stranger urges a girl to forget her lover; she will not. He tells her that Riley had been aboard his ship, and that Riley had been killed in battle with the French. She is distressed; he reveals that he is Riley and will never again leave her
The theme of a lover coming in disguise and testing his love is ancient; there is a version in Ovid's Metamorphoses (VII.685 and following). Cephalus doubts Procris, and (disguised by the goddess Diana) comes to her and tries to get her to be unfaithful to him. She utterly rejects his advances.
In that case, however, the ending is not happy. Although they are reunited, and happy for a time, she eventually starts to doubt him (prompted perhaps by his earlier doubts?). She follows him as he goes hunting, and he -- hearing a rustling in the leaves -- kills her with a cast of his javelin.
Even older, of course, is the version in the Odyssey. - RBW
See the notes to "The Plains of Waterloo (I)" [Laws N32] for Mackenzie's discussion of Laws N36 as source for "The Mantle So Green" [Laws N38] and "The Plains of Waterloo (I)" [Laws N32].
[On April 12, 1782], Admiral George Brydges Rodney defeated the French Admiral the Count De Grasse at the Battle of the Saintes in the Caribbean and brought the captured French ships into Fort Royal. (source} Moylan; _George Brydges Rodney, 1st Baron Rodney_ at the Wikipedia site). [See also Arthur Herman, _To Rule the Waves_, pp. 316-318; Herman notes that Rodney pioneered the attack from the leeward side, assuring that the French could not escape him by running; Herman also considers the battle to have re-established British naval dominance, which was not broken even in the Napoleonic Wars. - RBW]
Both Laws and Moylan make fight the battle between Rodney and De Grasse. Laws has Reiley serving on _Belflew_; Moylan makes it _Balflour_. Moylan notes "The Formidable was Admiral Rodney's own vessel. The Barfleur was the ship which captured de Grasse's flagship, the Ville de Paris." - BS
Brewster's version also mentions the Rodney/De Grasse battle; the ship in his text is the _Belle Flower_, though the date is April 10. Eddy has the date right; the ship is the _Belflew_. Cox also lists the _Belflew_ (and has the April 12 date); presumably their agreement was the basis for the name in Laws.