With runners at 3rd base (R3) and 1st base (R1), R1 is stealing on the first pitch to the batter. The defense has a "play on", so when the batter takes the pitch, the catcher throws to the shortstop (who is standing halfway between 2nd and 3rd base).

 

The shortstop makes a quick throw to 3rd base to try to catch R3 off the base, but the throw is wild and goes out of play. R3 is awarded home. At the time of the pitch, R1 was at first base. At the time of the throw by the shortstop, R1 was almost at second base. When the ball went out of play, R1 had rounded 2nd base.

 

Where do the umpires place R1?