Bolivia's getting a blood test for VPE, or viral propagated eclampsia, a serious condition that's dormant until pregnancy. Mothers and babies with VPE don't survive delivery. Since it killed Bolivia's sister and her child, it's very likely that she's a carrier.
Marilyn, Bolivia's mom, says that there's still hope. Bolivia argues that no one's ever survived. Besides, her life is hardly conducive to having a child. Marilyn wonders about the father; she just can't believe Bolivia picked up some guy while Frank was gone. Bolivia says that you and Lincoln should get together. He's not happy about this either.
Outside her apartment building, Bolivia tells Lincoln that she's being watched. (And indeed, someone's observing from across the street.) He sends a security detail. Inside, Bolivia seems to be alone. Then, BZZZT! She's shocked with a Taser by two men in black.
At Fringe Division, Charlie teases that Lincoln has a thing for Liv. That's ridiculous, says Lincoln. Although if she was gonna cheat on Frank with someone . . . it's none of his business. Charlie knew that was driving Lincoln crazy.
Brandon argues with Walternate about the need to experiment with children. The Secretary still says NO. Discussion closed. Lincoln calls Walternate and reports that Bolivia's been kidnapped. The Echelon satellite tracking system quickly locates Bolivia, who's strapped down in a delivery truck. Agents swarm the street where the truck seems to have stopped -- but Lincoln finds only a decoy transmitter. Someone has somehow mimicked Bolivia's signal.
Elsewhere, a medical team, wearing black scrubs and masks, straps Bolivia to a hospital bed. A bespectacled doctor, a blonde nurse, and the doctor's assistant stick a large needle into her abdomen. The nurse gives Bolivia a sedative pill, then turns on a light that shines a pattern of concentric circles on the spot where the needle went in. She angles a screen toward Bolivia and leaves. It's an alt-universe monitor, showing a 4-D image of the baby inside Bolivia.
Lincoln tells Charlie that this is either an inside job, or someone sold the tracker info to Bolivia's kidnappers. Farnsworth shows him an anomaly in the traffic around Bolivia's place: The same commercial vehicle drove past six times in the last week. Lincoln and Charlie investigate . . .
. . . and meet Henry Higgins, the cabbie who helped Olivia. Henry admits that he was checking up on her because he was worried. He wouldn't expect she would come back here. Lincoln says, "What do you mean, back here?" Henry explains that Olivia wanted to go home, to some guy named Peter. But when he ran into her a few weeks ago, she acted like she didn't know him. When he mentions the other universe, the guys put Henry in the SUV and discuss. Lincoln asks if Charlie remembers wondering whether their Olivia could have been switched with the one from other universe. You said that I was crazy, Charlie recalls. What if you're not, asks Lincoln.
Marilyn gets bad news: Bolivia's a carrier for VPE. Later, when she's called to HQ, she tells Charlie that Bolivia can't have the baby.
Lincoln reports Henry's story to Walternate. He asks, was our Agent Dunham replaced with theirs? Walternate calmly admits to swapping the two Olivias. He stuns Lincoln with the bombshell about the baby's father. He can't lose his future grandchild. He'll give Lincoln whatever information and access he needs to find her.
Bolivia is fully pregnant now. But she still attacks the nurse, fights off the other kidnappers, and bolts into the wet Chinatown night, trailed by the doctor's assistant. Wracked by a contraction, she slumps in agony. She staggers to a public phone and calls Lincoln. Explaining that they accelerated her pregnancy, she says talk to my mother. Lincoln orders the call traced, and Henry says he knows a shortcut.
Bolivia collapses amid a crowd of people. Charlie informs Lincoln about the VPE. Lincoln and Henry carry her into a shop. Lincoln holds her, and Henry introduces himself, saying he delivered his daughter in his cab, so he can help. Bolivia asks if Lincoln talked to her mom. He says just focus on this moment; it's you and me.
Bolivia is scared. Henry says push. She makes Lincoln promise to stay with her. He says there's no place else for me to be. Almost there. Lincoln says, "I love you." Bolivia says promise you'll save the baby. He cries and promises. And the baby's here! And he's OK! And so is Bolivia.
Laughing and crying, Lincoln says, "You have a son." "He's beautiful," says Bolivia. Outside, the crowd applauds. The blonde nurse walks away.
In the hospital stairwell, Charlie and Lincoln discuss the case with Walternate, who's carrying a huge bouquet. Shortly later, Lincoln muses to Charlie that the higher-ups put an impostor on their team, to protect the mission. And when Olivia came back, wasn't it about the time Broyles disappeared? It was, says Charlie. They wonder what else they don't know.
Bolivia explains to Marilyn that accelerating the pregnancy kept the virus from replicating as quickly. A nurse takes a blood sample from the baby. The man who collects the sample is the doctor's assistant!
In the stairwell, Walternate runs into this man, who says Walternate was right; speed trumped the VPE. He saved Bolivia. Walternate snaps, "You were careless," then hurries off. An Observer appears. "It's happening," he reports over his phone.
Walternate pauses outside Bolivia's room. Inside is a happy scene of mother and daughter, smiling over the new baby. Walternate smiles too.