The princess Andromeda was chained to a rock as a sacrificial offering to a sea-monster, to atone for the boasting of her mother Cassiopeia (standing at centre right). Perseus, riding on the winged horse Pegasus, slew the monster and set Andromeda free. This drawing was the model for an engraving by Goltzius’s step-son, Jacob Matham. The outlines were incised during the process of transferring the design on to a copper plate.