[umpjong]

Originally Posted by mbyron

Agree, but you forgot to take a runner off the bases. Let's stick with Able, Baker, etc.

Charlie bats first and reaches base.

Baker bats next, and the first pitch to him makes Charlie's at-bat proper. Baker reaches base.

The OP says that Able comes up next and the scorekeeper announces BOO before a pitch to him. (I agree with the consensus to shut up the scorekeeper.)

If a coach appeals at this point, he's right on time. The proper second batter was not Baker but Danny. So:

1. Danny, the proper batter for the spot where Baker batted, is out.
2. Remove Baker from base, but he's not out.
3. If Charlie's advance was due to Baker's at bat (not from a wild pitch, steal, etc.), he returns to 1B.
4. Since Danny made the last out, the next batter is Eddy.

This correct, my reply is only correct if there is a pitch to the third batter in OP, there was not so this, above, is correct...