Ice is the 4th episode of Season 4 and the 70th episode overall of the show Alias.Sydney and Vaughn are sent on a mission by APO to obtain a sample of a new bio-weapon, known as Ice 5, which can literally freeze a person to death. When the agents learn the substance is going to be sold to a buyer in Damascus, together Sydney and Vaughn have to turn each of the family members against each other while remaining undercover. But when they are found out, there are devastating consequences. Meanwhile Nadia asks Jack for the truth about her mother, and Sydney begins to wonder if Vaughn has really come to terms with Lauren's death.