 Jef wants to go angling on the day when Jeanne expects them to paint the windows, asks Odilon to lie, but he and Arnold stupidly blurt out the truth; Jef sneers the pair of idiots could be father and son, but Odilon, who knows the boy s mother well but never that intimately, starts believing so; since he hands out a welcome allowance and valuable gifts, Arnold willingly plays the part of his  lost son  (hence the title), as long as it doesn t become generally known. Lies invites Saskia to help her choose a present for Stef, so they uses various tricks to keep him at arms-length, while Filip insists Stef must firmly stand his ground or be domineered for life. When Jeanne tells him Lies is a good catch, good-tempered like her, Stef fears she ll become such a bossy dragon. Jeanne and Mimi think Jef is Arnolds illegitimate father; Odilon calls Arnold s real dad saying the man he is...