Two friends, Valentine and Proteus, are about to part. Proteus is the lover, Valentine the man immune to love. While Valentine goes out into the world, Proteus stays at home with his Julia. It is not long, however, before Valentine meets and falls head-over-heels in love with the beautiful Silvia. Joining his friend, Proteus meets Silvia - and, forgetting Julia, also falls in love!

The close friends are now rivals. Proteus sets about deceiving Valentine in order to win Silvia for himself. In the complex web of intrigue that follows, Valentine is banished, Silvia runs away and Proteus, with disguised Julia, gives chase.

At last, at a final meeting in the forest, the lovers are united and the play ends happily.