"The Mad King" by Edgar Rice Burroughs is a thrilling adventure set in the fictional European kingdom of Lutha during the onset of World War I. The protagonist, Barney Custer, an American unaware of his royal lineage, visits Lutha and is mistaken for his lookalike cousin, King Leopold. Barney's impersonation leads him into a complex web of political intrigue and romance, as he falls in love with Leopold's betrothed, Princess Emma Von Der Tann. The first part of the novel sees Barney foiling the schemes of the villainous Prince Peter and rescuing King Leopold, only to be forced to leave Lutha. The second part unfolds against the backdrop of World War I, with Barney returning to Lutha to save the kingdom from Austrian forces and ultimately, after numerous adventures and trials, taking Leopold's place as king and marrying Princess Emma, following Leopold's accidental death.