2 hot wires into light switch and no neutral
Belatedly -- from the OP's description, it appears that the original wiring was quite naughty and used the metal conduit as a neutral.  This'd explain the lack of a return current path once the conduit was cut back to repair the wiring insulation, which is also a no-no as you probably won't get it back together again without an excessive amount of work.

Not only does the OP need an electrician, the OP needs to warn their electrician about this lest they zap themselves unwittingly!  (A family friend of mine who is an electrician encountered a similar issue, only finding out when a conduit fitting arced as he went to repair it.)