It's the mid-90s, and rebellion is in the air. Skylark is an activist, a raver, a tree-dweller, a world-changer. Handsome, dependable Dan appears on the scene, offering her the security she has never had. When they fall in love, she shows him a new way to live; he will never be the same. But Dan has a secret, which Skylark must never, ever know. A secret so powerful that its fault-lines run from their ordinary council flat right up to the highest echelons of the state. Their story is the story of Britain's undercover police. As Skylark comes to doubt not only Dan's commitment to their shared ideals, but his very identity, she finds herself asking: can you ever really know the person you love?