Firewall - Henning Mankell

Stopping to use a cash machine one evening, a man falls to the ground: dead. A taxi driver is brutally murdered by two teenage girls who demonstrate a complete lack of remorse.
One girl escapes police custody and disappears without trace. Soon afterwards, a blackout covers half the country.
When an engineer arrives at the malfunctioning power station, he makes a grisly discovery...

Inspector Kurt Wallander is sure that these events must be linked - somehow.
Hampered by the discovery of betrayals in his own team, lonely and frustrated, Wallander begins to lose conviction in his role as a detective.

And somehow these criminals seem always to know the police's next move.