The watcher - Charlotte Link

Carla Roberts lives alone in the top of a highrise building in Hackney, frightened by the sound of the lift stopping and opening on her floor, with nobody getting out. Days later, she's found brutally murdered.

Meanwhile, Samson Segal, an unemployed thirty-something has taken to spying on his neighbours, particularly beautiful and successful Gillian Ward. When Gillian's daughter comes home to an empty, locked house, Samson takes her in but finds himself venting his anger in his diary when his good Samaritan actions go unappreciated, unaware that his suspicious sister-in-law cracked his password long ago...

When Gillian's husband is then murdered in his own home, Samson comes under intense scrutiny but the only man making any progress in the case shouldn't be working on it. Yet he's the only one who believes Samson is innocent...