I'm dealer, after picking up the turn card (Jack of Spades), I have this:
Naturally, I went alone with this hand.
First seat leads the Jack of Diamonds and third seat sloughs off. I take the trick with the nine of trump.
I lead back the right. First seat shows void, third seat plays the queen of trump.
Third trick, I lead the Ace of Trump. First seat sloughs off again, third seat stops the loner with the left.
The guy in first seat though starts chewing off his partner for not trumping that first lead. Third seat was holding the Queen-Spades and the Left (so a guarded left) with no other trump. If he would have trumped on that first lead, no matter what trump card he used, I would have made the sweep. He naturally rightly pointed this out.
I'm sure this is old hat to some of you, but it bears repeating. Against a loner, if all you have is a guarded left, you don't want to play the trump unless you either have last play or have already seen the right get played. A guarded left will always stop the lone, but only if you have last play (yes, if you have something like Left-Ace, this will stop the lone regardless of play order, but this is a general rule).
I was just stunned that first seat was ticked off at his partner for that, especially because both of them were highly rated players. Third seat played the hand exactly the right way.
Also kinda interesting how first seat didn't donate considering that he had no trumps and nothing that would stop the loner, while the turn card was the jack.