It is their motive, objective. He announces his intention and Varya enters. They're alone on stage and what ensues is very little dialog ending with a word or two about the weather. This is action, pained, wretched. It is about the death of hope, about repression.
Dramatic action is about stakes.
By knowing what's at stake for your character, you produce conflict. Conflict is action. The greater the stakes, the greater the action. If the stakes aren't high, the character won't care and if the character doesn't care, the audience won't care. Because these stakes are so very great, the audience will care very much about what happens in the play.