First two episodes lead you in then things rapidly get pretty disturbing and compelling in equal amounts a hard watch at times but the casting is first rate on this edge of your seat drama where you also end up wanting to slap the characters for doing blatantly stupid things! You’re forced to concentrate though with the excessive and at times annoyingly hectic timeline dipping, things being played out back to front but it just about works especially when watched back to back on BBC iPlayer. An emotional roller coaster ride from the safety of your armchair. Only downside is it actually happened.