>Neither enable me to guess what the next line executed would be.
It would be the line of code in the top-level program following the one that started the event handler. For example, if this is your top-level program:
*some code heredo MyEventHandler
*some more code here
where MyEventHandler issues READ EVENTS or calls some other routine that does, then RETURN TO MASTER would return to the *SOME MORE CODE HERE line.