A 23-year-old woman went out dancing in Boston Saturday night—and hasn't been seen or heard from since. Olivia "Liviy" Ambrose was with a group including her twin sister, friends from college, and fellow volleyball team members. Her sister, Francesca, tells MassLive Olivia was last seen around 10pm, dancing in front of the stage at Hennessy's, a pub on Union Street where live music is played. She then left the pub with a man who was escorted out by a bouncer; surveillance footage captures them leaving the bar around 11pm. Police have identified and contacted that man and determined he was not involved with Olivia's disappearance, but additional surveillance footage caught her walking with another man who approached her on the street about 40 minutes later, WCVB reports. Police are asking for the public's help identifying that man. (New hope 15 years after teen vanished.)