Languages like Korean allow internal arguments to bear accusative case morphology or nominative case morphology in desiderative constructions such as –ko siphta. Since the event-time of V–ko and that of siphta are different, the current research claims that –ko siphta is bi-clausal. Idiomatic expressions provide supporting evidence for the bi-clausal status. Nominative-accusative case morphology alternation is accounted for by positing an NP at the edge of a clause, while a coreferential null pronoun, pro, occupies the canonical object position in the embedded clause. The NP at the clause edge further moves to the matrix clause to satisfy the Case Filter.