Using Cell Value as a Worksheet Name in Formula

I wanted to use a cell's content as a sheet name, i.e.

and use the cell values (South, North, East, West) to reference cells from sheets called South, North, East, West like this:

=South!A1  =North!A1  etc. . . 

I wanted to use this to count all instances of TRUE in column A. My current implementation was inspired by a solution for Microsoft Excel and uses the INDIRECT() function, but it doesn't seem to work for Google Sheets:

=ARRAYFORMULA(SUM(IF(INDIRECT(A1)!$A:$A = TRUE, 1, 0)))