Calvin "Cal" Stone, also known as the Holy Grail, is a main character on Manifest. He is the twin brother of Olive Stone and the son of Ben and Grace. He was dignosed with cancer called leukemia. Cal rode the disappearing flight 828 with his father and Aunt Michaela. When the flight returned, five years passed. Cal along with other passengers have not aged and have gained a psychic ability. Out of all the passengers, Cal has the strongest psychic ability. At the end of Season 4, when they went back to April 7 , 2013 Cal became 11 again and didn’t remember anything that happened. He had his childhood back.