Gena Rowlands is running trying to escape the man with the gun who is threatening her and Hugh O'Brian. At one point, she is seen running barefoot since the terrain is rocky and difficult. You never see her or Hugh holding her shoes, but in the final scene when they arrive back at their car, she is wearing her shoes again.
There's a silencer on the revolver. Silencers do not work on revolvers because of the gap between the front of the cylinder and the frame of the gun which will allow the blast and sound from the firing of the bullet to escape and be heard.