Ovid recounts the story of Mercury and Argos in his Metamorphoses (I:668-708). The poet tells how Jupiter, in an effort to hide his infidelity from Juno, turns Io, the object of his lust, into a white heifer. But, so as not to be deceived, Juno requests the heifer as a gift from her husband and charges Argos, the 'all-seeing' watchman, with the animal's care. Jupiter, however, engages Mercury to free Io, which he achieves by lulling Argos to sleep with soothing music, before killing him. The composition here captures the moment when the watchman falls asleep, with Mercury reaching into the shadows with his right hand for the weapon that he will use to kill the sleeping Argos. The high quality of this beguiling work is evident in the delicate but sure handling of the paint, in the elegance of the drawing and in its tonal lyricism. The naturalism and lighting of the composition, which can be dated to the early part of the 17th century, might indicate a Caravaggesque influence, possibly the hand of a northern artist working in Rome at the time, when the city was flush with Dutch, Flemish and French artists. The attribution of the picture, however, remains uncertain.