Here's the link to a detailed recounting of the plot of this classic issue of Superman:
http://www.supermanhomepage.com/comics/pre-crisis-reviews/pre-crisis-mmrs-intro.php?topic=c-review-pc-sup88
As you can see, Luthor almost succeeded that time with his synthetic kryptonite, which he always seemed to have plenty of!
"if anything like this happened on the show I'd want Supergirl to defeat them on her own also (with Alex, Winn, MM supporting her in the background)."
And also Maggie - because you would expect the NCPD to get involved in the case, too.
"BTW Stewart, have you seen Supergirl: The Silver Age Vol 1 book releasing in July?. "
No, I haven't! Thanks for the link
Here's another classic early Toyman cover, Superman comics #44