The painting portrays an imaginary incident at the time of the St. Bartholomew's Day Massacre in Paris on 24 August 1572, when thousands of Protestants were slaughtered by Catholics. The subject itself was not new for Millais as he had treated it in 1852 in the painting, A Huguenot, on St. Bartholomew's day refusing to shield himself from danger by wearing the Roman Catholic badge (Makins Collection). In this work, Millais had portrayed the conflict in the form of an ill-fated love-affair between a Catholic and a Protestant, where the staunch Protestant is shown refusing the white cloth (the Roman Catholic badge) being tied around his arm by his Catholic lover. This act of refusal is an indication that he is prepared to die for his faith. In "Mercy": St. Bartholomew's Day, Millais shows the other side of the story involving the pious devotion of the Catholic who would kill for his beliefs. Millais's painting follows closely the requirements laid down prior to the massacre by the 'Order of the Duke of Guise', that Catholics had to follow: 'When the clock of the Palais de Justice shall sound upon the great bell at daybreak, then each good Catholic must bind a strip of white linen round his arm, and place a fair white cross in his cap'. This 'Order' was printed in the Royal Academy catalogue to accompany Millais's A Huguenot, mentioned above, when it was exhibited there in 1852.
In a gloomy interior, a man wearing a white arm-band, rosary beads around his neck, a crucifix fixed upon the brim of his hat and with his sword unsheathed, prepares himself for bloodshed. A Nun begs for '"Mercy"' on behalf of the hapless Protestants, but the man pulls her arm away and moves to follow the call to arms indicated by the Friar who beckons from the open doorway. The passion flowers and roses placed in the foreground appear overblown and withered. The passion flower was a recognised symbol for the suffering of Christ and was often used in Victorian art to indicate a doomed love affair. Here, the wilting flowers indicate that the pious fervour of the Catholic will have a tragic end. Millais viewed "Mercy" as a serious example of his late work, but it was not well-received by the critics. When it was shown at the Royal Academy in 1887, one critic declared that 'Sir John Millais disappoints expectations' and that his figures offered 'little else but meaningless violence of gesture' (Magazine of Art, 1887, p.272). Millais himself was disappointed with it and confessed to the artist Briton Rivière: 'I have done the picture ... I am sometimes happy over it, but oftener wretched' (Millais, II, p.196).
J.G. Millais, The Life and Letters of Sir John Everett Millais, II, London 1899.
Russell Ash, Sir John Everett Millais, London 1996, reproduced pl.40 in colour.
Tessa Murdoch, The Quiet Conquest: The Huguenots 1685 to 1985, exhibition catalogue, Museum of London, London 1985, p.314.