Donal Delaney is the caretaker of Castle Malloy.
Donal believes the Good People, who are fairies, caused the explosion at the castle so that Fiona would remain a little girl forever, and that they kidnapped Matt Simmons for trying to marry an Irish woman at the castle.
Donal is still overseeing the castle in 2008 when Matt Simmons disappears during his wedding preparations. Nancy soon discovers that Fiona is alive, and that she has been holding Matt hostage in her father's lab. Donal probably hadn't ever seen or heard her because he had never crossed the bog, and he mentions that his hearing is starting to go. Donal helps transfer Fiona to a nursing home.