An apparatus for automatically retracting a leash for an animal comprises a spool rotatably mounted in a housing for selectively winding and unwinding of a leash. The spool includes a hub defining an axis of rotation and gear teeth disposed about an outer surface of the hub. A gear train includes a plurality of gears operatively engaged with the gear teeth on the hub of the spool for rotation of the gears in the gear train. A carrier linkage defines a cavity for housing a portion of the gear train for rotation of the carrier linkage upon rotation of the gears in the gear train. A lockout pawl in the housing is movable between a first position that enables the spool to freely rotate and a second locked position to lock the spool against rotation. A cam surface on the rotating carrier linkage is configured to engage the pawl for moving the pawl to the second position. A control knob enables the gear train to be selectively positioned with the respect to the pawl to selectively predetermine the maximum length of
