INVISIBLE PREY In the richest neighbourhood of Minneapolis, two elderly women lie murdered in their home, killed with a pipe, the rooms ransacked, only small items stolen.  It's clearly a random break-in by someone looking for money to buy drugs.  But as he looks more closely, Davenport begins to wonder if the items are actually so small or the victims so random; if there might not be some invisible agenda at work here.  Gradually, a pattern begins to emerge - and it will lead Davenport to somewhere he never expected.  Which is too bad, because the killers - and, yes, there is more than one of them - the killers are expecting him