Toll Bridge — Aidan Chambers

To escape the pressures of suffocating parents and a possessive girlfriend, seventeen-year-old Piers takes a job as a keeper of a toll bridge and its cottage. There he befriends Adam, a charismatic wayfarer who shows up one day and refuses to leave. He also befriends a girl named Tess, and soon he and Tess find themselves strangely attracted to Adam and falling under his spell. The three test their sexuality and the bonds of their friendship as they discover who they are―and aren't―in a harrowing course of events that leaves all three wondering if you can ever really know anyone.
 
Like the other books in The Dance Sequence, The Toll Bridge can be read alone or as part of the series.