Shakespeare scholars agree that sources for the Hero-Claudio story in Shakespeare's Much Ado About Nothing include Ludovico Ariosto's epic poem, Orlando Furioso, published in English in 1591, and another epic poem, Edmond Spencer's The Faerie Queene, the relevant portion of which was published in 1596. As a frame of reference, Shakespeare wrote Much Ado About Nothing in about 1598-1599.
In Orlando Furioso, Polinesso, the Don John character in Much Ado About Nothing, is rejected by Princess Ginerva (the Hero character) because she's betrothed to Ariodante (the Claudio character), and Polinesso schemes to take revenge on Ginerva.
Between Geneura [Ginerva]and her faithful knight / Such discord and ill will he schemed to shed, / And put betwixt the pair such foul despite. / No time / should heal the quarrel he had bred; / Bringing such scandal on that damsel bright, / The stain should cleave to her, alive or dead: / Nor, bent to wreck her on this fatal shelf, / Counselled with me, or other but himself...." (Orlando Furioso, Canto 5, XXII)
Polinesso convinces Ginevra's maid, Dalinda (the Margaret character in Much Ado About Nothing) to impersonate Ginerva, and to appear on a balcony in sight of Ariodante, so Ariodante can be witness to Ginerva's supposed infidelity with another man.
In Much Ado About Nothing, one of Don John's accomplices, Borachio, meets with Margaret, disguised as Hero, but in Orlando Furioso, Polinesso himself climbs a rope ladder to meet on the balcony with the Ginerva impersonator, Dalinda.
Interestingly, this story is told in the poem by Dalinda, Ginevra's maid.
When Polinesso climbed the stair, which I / Cast down to him, and scaled the gallery.
Arrived, my arms about his neck I throw, / Weening that we unseen of others meet, / And kiss his lips and face with loving show, / As him I hitherto was wont to greet; / And he assayed, with more than wonted glow, / Me to caress, to mask his hollow cheat. / Led to the shameful spectacle, aghast, / That other [Ariodante and his brother, Lurcanio], from afar, viewed all that passed... (Orlando Furioso, Canto 5, L, LI)
In The Faerie Queene, the story is told from the perspective of Phedon (the Claudio character), one of the lovers.
Equally interesting is that in The Faerie Queene and Much Ado About Nothing, the maids—Pyrene in The Faerie Queene and Margaret in Much Ado about Nothing—are portrayed as relatively innocent, unknowing participants in the revenge plot. Both Margaret and Pyrene were deceived into believing that their impersonation of Hero (in Much Ado About Nothing) and Claribell (in The Faerie Queene) was a harmless "conceit," or a game being played by them and their own lovers.
In Much Ado About Nothing, Leonato holds Margaret accountable for her part in the plot against Hero, but excuses her as being deceived by Borachio.
LEONATO. ...But Margaret was in some fault for this, / Although against her will, as it appears / In the true course of all the question. (5.4.4-6)
Earlier in the play, Borachio also relieved Margaret of responsibility for the deception.
LEONATO. ... This naughty man [Borachio] / Shall face to face be brought to Margaret, / Who I believe was packed in all this wrong, / Hired to it by your brother.
BORACHIO. No, by my soul, she was not; / Nor knew not what she did when she spoke to me; / But always hath been just and virtuous / In anything that I do know by her. (5.1.288-295)
Also, in Much Ado About Nothing, it is Borachio, not Don John who devises the plot to deceive Claudio.
BORACHIO. Go then; find a meet hour to draw Don Pedro and the / Count Claudio alone; tell them that you know that Hero / loves me; intend a kind of zeal both to the prince and / Claudio, as—in love of your brother's honour, who hath made / this match, and his friend's reputation, who is thus like to / be cozened with the semblance of a maid—that you have / discovered thus. They will scarcely believe this without / trial. Offer them instances; which shall bear no less likelihood than to see me at her chamber window, hear me / call Margaret, Hero, hear Margaret term me Claudio; / and bring them to see this the very night before the / intended wedding—for in the meantime I will so fashion the matter that Hero shall be absent—and there shall appear / such seeming truth of Hero's disloyalty that jealousy shall / be called assurance and all the preparation overthrown. (2.2.29-43)
In Orlando Furioso it is Polinesso (the Don John character) who devises the plot against the lovers, and who carries it out himself.