By Brandy McDonnellGrammy-winning a cappella group Pentatonix, which recently released its fourth holiday album, "Christmas is Here!," returns to NBC for its third holiday special with “Pentatonix: A Not So Silent Night,” airing at 9 tonightAs previously reported, the multiplatinum-selling vocal quintet, which includes former University of Oklahoma student Kirstin Maldonado, embarks on the special on an unforgettable journey throughout Las Vegas, making stops along the legendary Strip including the iconic Caesars Palace and the stunning Eiffel Tower at Paris Las Vegas, according to a news release.