Pentax IQ ZOOM 115M Operating Manual page 25

Rewinding a film in mid-roll
If you wish to unload a film before exposing all
the frames, push the mid-roll rewind button with
the protrusion part of the strap ; the lens retracts
and then film rewinding starts. When rewind is
completed, the motor stops, and ( u ) blinks, indi¬
cating that the back cover may be opened safely.