Mark's holiday plans, playing Blitzkrieg, getting to grips with the Roman Empire and learning the clarinet, are rudely interrupted when his sister, Sarah, turns up after splitting up with her husband. Sarah's incessant chatter and alarming similarities to her brother soon lead Jez to conclude she's not 'the one', and he embarks on a campaign to win Suze back. Which leaves Mark having to dump his sister for Jez.