In what way does this scene bring together the central ideas that Tennessee Williams is communicating through the play?

Certainly the glass unicorn comes in this scene as a unifying element of many of the themes. The glass unicorn, of course, is a clear symbol for Laura. She, like the unicorn, is odd and unique. Both Laura and the unicorn are fragile -and Jim "breaks" both of them. Laura's subsequent gift of the broken unicorn, however, suggests the extent of her affection for him. For Jim, the evening has been insignificant. But Laura has harbored a girlish crush on him for many years - she even saved the program of the play in which he starred - and the gift of the unicorn, an item that is a symbol of herself, shows how much she still likes him. It is the gift of an odd and painfully shy girl, for whom kissing Jim (probably her first kiss) was a climactic experience.