Colin is asked to be best man at Trevors wedding which he reluctantly accepts.
At home he writes the best man speech but Jen doesn't find it funny.
He throws a stag party for Trevor but the following morning Colin is distressed because he can't remember where he put the ring. He turns his flat upside down but it turns out to have been around his neck on a piece of string the whole time.
Colin delivers his speech at the wedding to deafening silence so ends up having a rant at everyone.
At the flat Colin wakes up on the settee and thinks its all been a dream. Jen eating some wedding cake informs him that its been anything but.

Colin and Jen are at a wedding. Colin is bored and involuntarily shouts out when the vicar asks if anyone knows any impediment to the marriage.

When they get home they laugh about Colin's indiscretion. Colin remarks that they should never go to another wedding again. He opens the mail and it's a wedding invitation.

At work Colin thanks Trevor for the invitation and Trevor asks him to be his best man. Colin his horrified but says yes anyway. Trevor then asks Colin to tell Graham he's not invited. He tells him whilst they are at the urinals. Graham rants at Colin. Later Trevor tells Colin Graham is invited.

At home Colin struggles to write the best man's speech. When he finally does so Jen doesn't find it funny. Colin says he's not going to do it now but Jen threatens him with physical harm if he pulls out.

Graham and Colin organise the stag night which is completely flat. In desperation Colin invites them back to his place. He books a stripper and they all get drunk.
The following day Colin realises he's forgotten where he put the ring. Jen comes back to a flat that has been turned upside down due to Colin's desperate searching. Colin shows her the ring tied around his neck [where it was all the time] and says 'I've found it'.

At the wedding Colin's speech is greeted by silence throughout and he finally snaps and rants at everyone in the room.

Back at the flat Colin is asleep on the sofa and is having a bad dream. He wakes up and says 'Thank God it was just a nightmare'. Jen is sat at the table eating wedding cake and turns and smiling says 'No it wasn't'