For the subject see Ovid, 'Metamorphoses' (1). Daphne, pursued by Apollo, cries for help to her father, the river God Peneus. He transforms her into a laurel bush as Apollo reaches her.
A fine compositional study in pen and ink survives (Windsor, Royal Collection). While the landscape is the finest in the series and was probably made by Domenichino himself, the authorship of the figures is less secure and may have been assigned to an assistant.