Billie Duncan is a new teacher at waterloo road. Her older sister Megan is also a teacher. Billie is excited to be working a long side her sister again. Billie soon meets tom clarkson and things get complicated when she starts to like him. Tom is also Megan's boyfriend. Billie and Tom soon end up in bed together and start an affair. Billie feels bad with what she is doing to her sister. But little does she know that Megan is tooling around with her so called best friend max Tyler, behind Toms back. Billie and tom start an affair together and even though Billie feels bad about it. She can't help but be resisted to tom. How long can Billie keep up having an affair with her sisters boyfriend? and will Megan forgive her sister when she finds out the truth?