Barney and Robin's romance falters, and Lily comes up with a scheme to break up the unhappy couple that involves a little help from Robin's celebrity friend, Alan Thicke (who appears in a cameo).

Audrey pours on the guilt when Jeff takes off for an Atlantic City getaway, but Jeff discovers that Audrey's the one who has something to feel guilty about.

Charlie and Alan wake up together...with a woman they don't recognize.

Sheldon enters a trading-card competition when he hears Wil Wheaton (in a cameo), for whom he harbors resentment, is also participating. Meanwhile, Wolowitz asks Penny to set him up with one of her friends.

The lab is attacked and new CSI Jesse Cardoza is taken hostage along with four other people. Horatio must carry out the gunman's unique request in exchange for their lives.