In one case, I heard divorced parents who conspired to lie to their children. They agreed not to tell their teenage children that the father had been diagnosed with cancer. They reasoned it might be cured, in which case the children would have been unnecessarily concerned. A seemingly benign mission with possible disastrous results. They had given no thought to the possibility that the children would sense a tension, and that without any explanation being provided, they could well worry more over the silence than they would about the truth.
Parents often conceal that they have decided to divorce.
The father went home after work for dinner as always. He stayed at the family home until after the child had gone to bed. It was an elaborate deception. When the truth is finally told, the child has to cope with whatever unpleasantness is part of that truth, but the child will also have to sort out self-doubt from mistrust. Moreover, the child will always wonder what else the parents might have lied about and when the parents might lie again.