It was a double ep, episode summaries below:
Ep 21 - Second Double
Fake Francie tells Sark that the CIA is on a mole hunt; Irina doesn't want Will killed, but she does want him to be convincingly framed. The setup works as Jack and Kendall believe that Will is the second person who was genetically reprogrammed to look like someone else. Even Sydney has her doubts that he isn't a fake. Believing that Francie needs to be protected, Syd tells her that she works for the CIA. In an effort to find more info about the second double, Syd and Vaughn follow a lead that reveals the location of the data they seek. Meanwhile at the CIA, Kendall arranges for Will to be transferred to another location for unrestricted interrogation; Sark sets up an ambush so that Will can be extracted and killed. The attack doesn't go as planned, and Will is able to escape. Jack is approached in a very public place by Sloane, who says that he forgives Jack for his betrayal at SD-6. He also wants Jack to consider returning to their partnership. Jack refuses, but Sloane leaves vowing that they will work together again. On a second mission, Sydney goes to get the data that can exonerate Will, but Irina gets there first. She erases the data, telling Sydney that she will have to help her in order to get it. Elsewhere, Will has called the only person he thinks he can trust: Francie. She picks him up and drives away.
Ep 22 - The Telling
Irina sends the CIA information about the double's DNA; after Will is caught, tests prove that he isn't the double. As Syd skates at an ice rink, Irina shows up, telling Syd the location of Sloane's Rambaldi artifacts. Investigating the name that was include with the DNA data, Will discovers that the double was one of twenty children involved in Project Christmas. When the warehouse that Irina spoke about is revealed to contain fakes, the CIA realizes that it's a set up. Unfortunately, part of the set up involved an attack on Jack and his party as they transported the Di Regno heart. Jack wakes up in a dimly lit room where Sloane joins him. Sloane announces that a Rambaldi device called The Telling is almost complete, and he speaks about a coming change. Irina calls Syd swearing she didn't know that the artifacts had been moved; she tells Syd where to find Sark, who will know where Sloane is. Syd and Vaughn go after Sark; captured, he reveals that Jack and Sloane are in Mexico City. The CIA raids the location per Sark's instructions. Irina shows up during the raid and announces that it's Sydney, not Irina, who is the one Rambaldi spoke of, and that only she can stop Sloane. Irina wishes Syd luck before making a daring escape. Meanwhile at Sydney's apartment, Will finds evidence that Francie is the double. He calls Sydney, leaving a desperate, whispered message until a noise interrupts him. He's attacked by the imposter, and they fight briefly until she stabs him. Later Syd comes home to find fake Francie sitting calmly on the sofa. Unaware that anything is wrong, Syd begins to eat ice cream as she checks her messages. She listens to Will's message without reacting; she hangs up and offers Francie a bite. When she accepts, Syd knows she's a fake, because the real Francie hated coffee ice cream. Francie realizes her mistake and follows Sydney, who went to retrieve her gun. They battle for several minutes before Sydney shoots the double. Syd passes out. She wakes up - wearing different clothes - in an alley in Hong Kong. She makes her way to one of the safehouses, where Vaughn joins her. He tells her that Will is okay, then pauses, not knowing where to begin. Sydney notices Vaughn's left hand and asks why he's wearing a ring. He tells her that she's been missing for almost two years.
Yeh they're a bit length... I'd rather watch the ep