The Forbidden Door book by Dean Koontz

‘I will come for you. Nothing can stop me!’

Rogue FBI agent Jane Hawk is on the trail of the members of a murderous organization who drove her husband – and scores of other fine individuals – to commit suicide for no explicable reason.

Now the secret cabal behind the plot is closing in on her beloved five-year-old son, whom she sent into protective hiding with her dearest friends.

Jane will stop at nothing to save him. But even if she can get to him in time there's still the risk that the forbidden door will be opened and an unimaginable terror unleashed.