When Cassie was a little girl, her beloved Grandma Dottie gave her the cream-colored prom dress she wore to her own junior prom in the 1950s.

Dottie assumed Cassie would use it for playing dress up; she had no idea Cassie put it away in her closet and would keep it for many years to come.

Years later, on the night of Cassie’s high school graduation in California, she decided to wear that very same prom dress. Thanks to her grandmother’s style, the teen had fallen in love with vintage clothing, so the outfit was totally perfect for her.

Dottie, meanwhile, had no idea what Cassie had planned. The sneaky teenager told the rest of her family about the surprise but kept her grandmother in the dark.

While visiting for the graduation ceremony, Dottie kept asking to see Cassie’s dress. She was told it wasn’t there at the house, but at one of Cassie’s friends houses. She was disappointed to not get to see her beloved granddaughter in her evening wear.

But then something unexpected happened. All of a sudden, Cassie stepped outside to reveal her dress to Dottie.

“Needless to say, there were lots of tears from everyone!” Cassie’s aunt wrote on YouTube. Watch the video to see how emotional the whole thing was.