Possibly forgotten solution to pen tool problem-?

I may have known how to solve this in years past, but here's the problem I can't solve now: I'm in Illustrator 21, tracing with the 4-option (P) pen tool. over a photo with a lot of long straight lines. When I get to the end of  a straight line, I don't know how to simply STOP the line. If I stop the pen tool moving, then hit click (Wacom), or  click plus -Command, or  -option, or -Control, or -Retrun, any or all of the above, I will create an anchor point, but it's an anchor point for what is clearly intended to be a curved pen line continuing on beyond the anchor point. In other words, the line is in no way stopped. So what keyboard shortcut or command will simply stop the line? End it?  How do I do that?