The Seahawks had a chance to close the gap, but Austin Booker deflected Myers' 33-yard field goal attempt early in the fourth quarter, preserving the Bears' two-score lead.
Seattle closed the gap to 20-17 on Darnold's 7-yard TD pass to receiver Cooper Kupp coupled with a two-point conversion pass to Horton with 11:46 left in the fourth period.
The TD came after linebacker DeMarcus Lawrence forced and recovered a Colston Loveland fumble at the Bears' 25 following an eight-yard reception.
Two plays before the touchdown, it appeared that the defense had stopped the Seahawks again when Cam Lewis intercepted a Darnold pass in the end zone. But the takeaway was nullified by a defensive holding penalty on Clark Phillips III.
On their next possession, it appeared that the Bears would have to punt when Swift was tackled for a 2-yard loss on third-and-4 from the Seattle 39. But the play clock had expired before the ball was snapped, drawing a delay of game penalty.
On the next play, Kalif Raymond caught a quick pass from Williams on the line of scrimmage and darted up the middle for a 39-yard gain to the 5. Swift then raced around right end for a 5-yard TD that gave the Bears a 27-17 lead with 8:28 to play.