Will Karen and Doug's cheatin' hearts tell on them, or will Leo? Meanwhile, Isabel ain't misbehavin' but feels guilty anyway when she runs into Everett while jogging; and Jennifer receives an ominous letter from one of her professors.

As Valentine's Day approaches, Leo is strung out with work, and Isabel goes out to a concert with Everett. Meanwhile, Alan notices that his wife is "glowing."

Everett finds an apartment for Isabel; Leo's grandfather has a heart attack; and Karen admits to Alan that's she's seeing someone.