Charlie's girlfriend, Chelsea, gets sick in the middle of the night and Charlei's first reaction, of course, is to send her home.  Charlie let's her stay and when she passes out, Alan gives him the wise advice that when he asked Chelsea to get engaged he was agreeing to take her in sickness or in health.  Charlie goes to sleep and wakes up to Chelsea with a very scary, irritate red face.  Chelsea send Charlie out to the pharmacy to pick her up about a million different medicines.. and tampons.  

After a fun and embarassing trip there with our favorite pharmacist, Russell (Martin Mull), Charlie is then sent to Chelsea's apartment to pick up clean clothes and take care of her cat, Sir Lancelot.  Charlie forces Alan to drive him after he's had too much cough syrup and bourbon.  After paying Alan to clean up Mountain Lion-sized poops in the litter box, Charlie comes home and gets sick himself.  He ends up having a nightmare about a life-sized Sir Lancelot using his toilet and thinks he's not going to make it through the night.

Meanwhile, Jake is dating a nine year old at school that he's using to help him with his math homework.  Yes, sadly they are in the same math class and no, she is not an advanced student.

Also, while Charlie is out, Berta comes in to take care of Chelsea, but makes Chelsea promise not to let Charlie know she's actually nice.  She's worked hard to make Charlie expect so little of her.