When Lord Marchmain invites Sebastian and Julia to visit him and his mistress Cara in Venice, Lady Marchmain encourages Charles to go with them in the hope that he can act as a positive influence on her son. Increasingly interested in Julia, Charles surreptitiously kisses her in a dark alley, unaware that Sebastian can see them from the other side of a canal. Jealous of his attention to his sister, Sebastian sets out to end this friendship, and on their return to Britain, Lady Marchmain makes it clear that Charles cannot marry Julia since he is not Catholic and professes to be an atheist.