The highly rated defender has penned a deal with the Glovers until the end of the season after signing a one-year contract extension with his parent club.
This will be Stephen's second loan stint in the green and white after spending the majority of last season at Huish Park.
During his spell last season the 6'5" defender made over 30 appearances including an impressive performance against Premier League Manchester United in the third round of the FA Cup.
Manager Paul Sturrock said: "I am very pleased with the acquisition of Stephen. For a young player he was outstanding in the heart of the defence for us at the end of last season.
"He is going to be the stalwart of our defence this season. I am really looking forward to working with him and helping him to improve his game."