A drawing of Mercury about to bring his sword down on the sleeping Argus. To the right, a smaller scene of Mercury charming Argus to sleep with his pipe, with Io transformed into a heifer. In the clouds, Juno in her chariot drawn by peacocks, Jupier possessing Io, and Jupiter instructing Mercury. 

Popham (in P&W): The figure of Mercury is taken with slight modifications from that of Hercules in Caraglio's engraving of Hercules and the Lernean Hydra (Bartsch XV, p. 85, no. 46). There is also a relationship between this composition and that of a drawing in the Albertina (with an old attribution to Lorenzo Sabatini; Höper 1987, no. A350) which likewise represents incidents in the story of Io, the main one being Mercury charming Argus to sleep; that sheet is of approx the same size (33.5 x 48.5 cm) and shows the same relationship between foregrounf and background incidents. The two drawings cannot however be pendants - apart from the difference in technique - as some of the same incidents are reproduced in both. The style of the Windsor drawing suggests Bartolomeo Passarotti, but is not absolutely conclusive. 

C. Höper (1987, no. A363) classed the drawing among the followers of Passarotti.