That's definitely true of live theater -- I never had to do it,
thankfully, but in stage management classes, we're instructed that if
we ever get news of the death of anyone close to an actor or a
significant member of the crew during the performance, we don't tell
the performer -- or anybody else in the production, for that matter --
until after the performance. You don't have to lie -- mainly because
death is almost always unexpected and therefore there are few
circumnstances in which anyone, much less an actor, could be expected
to expect it -- but you do have to sit on the news, even if it was
communicated to you an hour or two *before* the performance. Even when
there's understudies -- understudies are used in different ways by
different companies and, moreover, they most often aren't pinch
hitters or relief pitchers, they're substitutes swapped into the
starting lineup. On Broadway or in L.A. (or Chicago), for instance, an
understudy might not even be there for every performance and might
even have gotten another gig for that day/night (a concert, a
commercial, an audition, maybe even a day-player role on a TV show).
On the other hand, there's Florence Henderson and The Brady Bunch.
Sherwood Schwartz was just being a pissant, control-freaky little
fuck. Even back then, schedules could and would be worked around.
-- Rob