Sapphire Stone, aka Joule, is the time-traveling string theory counterpart of Vector, one half of the Time Twins and member of the PRIME SUMMER PROGRAM. She is sometimes known as Sappho to her friends. As best she can recall after her time traveling, she comes from a better timeline than her counterpart, and was sent back by her father Biff Roberts to stop some sort of collapse of the alternate timelines to a single darker timeline which she believes is being engineered by some supervillain, but she can't remember who or what it was. Joule chose to focus on helping her twin with his mission to make sure Biff and their mother (who neither of them could remember) got together and stayed together. After some initial friction, Sapphire and Jack Flash were able to come to a temporary understanding, but that became frayed during the team's final confrontation with the Antediluvian in the parking lot of the Parthenon restaurant. With emotions running high and Jack's nemesis K-Train making an appearance, Sapphire and Vector broke from the team and left, seemingly kidnapping their father and leaving Jack Flash and Eclipse to deal with the Antediluvian.