For their science project, Screech and Kelly construct a machine which is supposed to reveal the compatibility between two people. It causes problems, however, when it seems to confirm Jessie's suspicion that Slater still has feelings for his old girlfriend, Jennifer, who has just moved to town. To add even more complication, Zack develops a crush on Jennifer, but she's still preoccupied with Slater.- Written by Anonymous
A girlfriend from Slater's past transfers to Bayside, and Jessie gets upset. Screech's science experiment proves that old feelings die hard.