Sealed with a Kiss (S02E08)

Title: Sealed with a Kiss Plot: At the school dance, Erica encounters an older boy and shares a passionate kiss with him in a secluded stairwell. Soon after, she starts to feel unwell and suspects he might have passed on mono. When he visits her at home, Erica is too ill to join him, so he invites her twin sister, Heather, for a drive, where he kisses her too. Heather fills Erica in on the unexpected turn of events, prompting the sisters to visit the doctor to check for mono. They breathe a sigh of relief when they learn Erica only has the flu.