Spock - both Spocks - have some profound and brilliantly-written dialogue in this one. The emotion's so strong there, even when it's being contained with iron discipline. Especially from the elder Spock - there's warmth and wisdom and love in the way he speaks to his old friends, even though we never actually see him smile. You can feel it in his words. The same's true with the younger Spock, when he's trying to contain his rage and despair.