I get the impression Lass was perhaps leaving SF to get away from someone. Or someone thought so.

Unless she was a lesbian, she likely had male dates.

Possibly she was somewhat involved with someone at Letterman.

Or someone was very much "infatuated" with her without reciprocation.

Could have been anyone from a doctor to a hospital janitor.

Thinking about this case for twenty years…..I just don’t see it as a serial killer type scenario.

The Zodiac? No. Not even close.

Who sent the Pines letter? Her SF-based killer who wanted to pass the blame onto a current serial killing maniac?

Who called for Lass the day after she disappeared? Not many serial killers call as he did unless they are taunting (not really the case here) or buying time.

To me, this has the marks of someone who knew Lass or was at least personally acquainted with her.

I think she left SF either to get away from this person, or for whatever reason and he took it very "poorly".

He may have followed her up to Lake Tahoe, stalked her, made notes of when she came and went and where she lived.

Perhaps he already knew through mutual acquaintances.

The night she drove back home, he was waiting and ready.

No other scenario makes much sense.

Some suggest she just disappeared. I doubt this for many reasons but it’s a possibility.

Many cases over the many decades look like this one.

A woman seeks a new life in a new place only to have old men in her life decide she was not going to "leave them" or get away.

To me, this smells more like this scenario than any other.

FWIW.