Cassandra Berry accepts a lucrative offer—massive payment and guaranteed college admission—to seduce a brilliant man and conceive his child. The plan appears foolproof. Until she meets Harry Xavier Devon. A two-time Fields Medal winner and celebrated mathematical prodigy, Harry immediately deciphers his brother's desperate scheme. His sibling needs an heir for his empire but lacks the ability to father one, banking on Harry's cooperation. Harry refuses to be manipulated. Instead, he flips the game. Doubling Cassandra's fee, he coerces her into maintaining the illusion of intimacy while his brother remains deceived. Harry believes he's orchestrated the perfect revenge—until Cassandra disrupts every calculation he's made. She's no meek accomplice or gold digger. She's relentless, unapologetic, and impossibly magnetic. One summer confined in the same house becomes a collision neither anticipated. Harry, accustomed to solving impossible equations, discovers that passion defies all logic. And Cassandra proves that some variables can never be controlled—especially when a brilliant, possessive billionaire is determined to make her his.