Anne,
I know it's not "The Source" because I just watched it today, and nothing like that happened.
The episode you're talking about is "Chi of Steel", when Jonathan and Martha exchange chores while they are in Metropolis. Martha sits around drinking coffee (or tea), playing checkers, etc., while Jonathan has to buy groceries, iron the clothes, cook dinner (purchased Chinese food), etc.
malu
EDIT: Oops! Took too long to type this, and Pam got ahead of me.
On "The Source", Martha and Jonathan ate the drugged Chinese food, while Stewart was "murdered".