The storyline follows the pregnant Olivia Dunham of the parallel universe ("Fauxlivia") as she experiences a kidnapping and acceleration of her pregnancy; meanwhile, her fellow Fringe agents Lincoln Lee and Charlie Francis attempt to locate her.

"Bloodline" featured the return of guest actors Seth Gabel, Kirk Acevedo, Ryan McDonald, Andre Royo, and Amy Madigan.

"Bloodline" received mixed to positive reviews from critics, with several commentators characterizing the kidnapping mystery as predictable while also praising the depth of the parallel universe and its characters.

Lead actress Anna Torv submitted the episode for consideration at the 63rd Primetime Emmy Awards, but failed to receive a nomination.

By the time they arrive, Fauxlivia has been kidnapped; though they try to follow a secret tracker each agent carries, her abductors have extracted it to throw Fringe off their tracks.

Astrid Farnsworth (Jasika Nicole) identifies a vehicle that has passed by Fauxlivia's home at a high frequency, that being the taxi that belongs to Henry (Andre Royo).

"Bloodline" was co-written by co-executive producers Monica Owusu-Breen and Alison Schapker, while The Practice veteran, Dennis Smith, directed the installment.

[7] Previous guest stars Seth Gabel, Kirk Acevedo, Ryan McDonald, and Michael Cerveris returned as Lincoln Lee, Charlie Francis, Brandon Fayette, and September the Observer, respectively.

[1][16] Also within the parallel universe, the movie Taxi Driver is shown to have been directed by Francis Ford Coppola rather than Martin Scorsese (though Robert De Niro was still able to improvise the "You talkin' to me?"

[1][16] "Bloodline" aired the day after Fringe's fourth season renewal was announced by Fox Entertainment,[15] which came in the wake of various actors communicating directly with fans to watch the series.

"[1] Entertainment Weekly staff writer Ken Tucker called the episode "a beautifully modulated hour, written by Alison Schapker and Monica Owusu-Breen, that took care to establish the anxiety felt by Altivia and her mother, Marilyn (Amy Madigan) about the pregnancy.

"[20] IGN's Ramsey Isler also didn't find the birth storyline all that shocking "since the number of people that had the power and knowledge to do this kind of thing was low.

"[21] Rating the episode 7.5/10, Isler added that "the story could have used a bit more misdirection and a red herring or two to really keep us guessing, but that's a minor critique.

"[21] Some television critics have praised the parallel universe's characterization,[15][20][21] with one noting that the "writers have made us care about the other side of this war, forced us to see the opposite numbers of our heroes as real and human and sympathetic; it's a brilliant move.

[1][15][21] Anna Torv submitted "Bloodline", along with the season three episodes "Olivia", "Entrada", Marionette", and "The Day We Died", for consideration in the Outstanding Lead Actress in a Drama Series category at the 63rd Primetime Emmy Awards.