Susan stands up for Caspian, when he feels outranked by Peter. This is not something Susan would do for anybody. The thankful/amazed look he gives her as she argues with her own brother speaks volumes of the bond forming between these two.

Susan tries to persuade Caspian not to kill his uncle during the Castle Siege, after the Prince finds out he killed his father. In the end, the desire for revenge is stronger than Susan's words, but it does make him hesitate for a moment, enough for Miraz's wife to shoot him in the arm.

After nearly being seduced by the power of the White Witch, Caspian looks back to see Susan looking at him reaprochingly, as if he has disappointed her. She walks away without a word and the look in Caspian's eyes speaks of a terrible sadness.

When Susan must escort Lucy to find Aslan, Caspian makes sure that they are secure in their saddle. He wants to give her back her horn, but she refuses saying that he "might want to call her again" and smiles shyly. The prince looks amazed at the woman in front of him, a plan to help her already forming in his mind.

 After sending Lucy to find Aslan on her own, Susan battles the Telmarine soldiers that were following them. The Gentle Queen uses her bow expertly until she's knocked down by one of the soldiers. She thinks she's going to die until out of the blue Caspian appears and defeats the remaining attackers, offering his hand to her, he says "Are you sure you don't want that horn?" Susan smiles.

Susan falls down the cliff during the Telmarine attack, she's held by Trumpkin and manages to get to safety. In the distance, Caspian and Peter look at her with despair.

After the battle, Caspian sees Susan and Peter walking with Aslan. She looks distant, lost. He speaks to them, announcing they are ready and the look he gets from the Queen is one of great sadness and regret.

The Pevensies offer to go back through the tree-trunk to show everyone that is safe. Peter gives Caspian his sword and the now king tells him he will look after it until he returns. Then Susan reveals that Peter and she will not be coming back. Caspian is shocked and in clear agony, wishing they had had more time. Susan walks up to him and says they would have never worked anyway, because she is 1300 years older than him. She turns to leave, but her logic fails her for once as she moves back to the sad king and kisses him briefly but passionatley. Their last goodbye.