The forbidden door / Dean Koontz.

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. After discovering their plan to subjugate the world by means of an insidious new technology, she has been hunting them down one by one. Now she is America's most wanted fugitive and the organization is closing in on her beloved five-year-old son whom she sent into protective hiding with her dearest friends. Faced with insurmountable odds, but armed with a mother's love for her son, 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.