Northampton have announced the signing of centre-back Rod McDonald.
Bolton forward Rob Hall has returned to MK Dons on loan.
The 24-year-old, who can feature at left-back or centre-half, has left Falkirk on a Bosman free transfer.
Scobbie had spent his whole career with Falkirk but has now opted to move to the top-flight.
He will compete with Callum Davidson for the left-back berth at McDiarmid Park.
Falkirk have moved quickly to replace him, signing Luke Leahy from English non-league outfit Rugby Town.