McWilliams-Franklin scored half of her 12 points in overtime to lift the Sun to a 71-67 victory over the Detroit Shock.
Detroit had a five-game road winning streak snapped. That run started with a 74-73 victory here on June 6 against the Sun, who were swept by the Shock in last year's Eastern Conference finals.
Connecticut started the extra session with six straight points to snap a 61-61 tie, including a basket by McWilliams-Franklin with 3:03 left. She added the final four points for the Sun.
Nykesha Sales collected 22 points and 10 rebounds and rookie Lindsay Whalen handed out 10 assists for the Sun. Sales made two free throws with 13 seconds to go in regulation for a 61-61 tie.
Swin Cash, who starred at the University of Connecticut, led Detroit with 22 points. Ruth Riley scored 13 points, including all six of the Shock's in overtime. However, she missed a potential game-winning shot at the end of the second half.
The teams meet in Detroit on Sunday.