The Adventure of Auld Lang Syne

The time: 10:00 pm, New Year's Eve, 1947. The place: The ballroom of the Hotel Astor. The victim: Mr. Marcus Halliday. And the suspects (all the usual ones): the son (and his gold-digging girlfriend), the untrusted nephew, the long-time secretary (and her brand new fiance), and the new business partner (of course, stealing from the company behind the victim's back). The soon-to-be victim has just announced that he plans to disinherit all of the above before the night is out - only to be found minutes later, slumped over in a nearby phone booth. Can Ellery figure out the clues as they play out? Of course, he can. But can you?