6/6 The three finalists' last challenge comes with a fiendish twist.
5/6 The groups must create a video with the potential to become an internet hit.
4/6 Gareth concludes his training with expert help and a new focus on performance technique.
3/6 Gareth brings the surviving groups together for the first time.
2/6 Gareth mentors the next four a cappella groups.
1/6 Gareth mentors the first four a cappella groups before they perform to a live audience.