"A Tale of Two Cities" is the third season premiere, and 50th episode overall, of the American Broadcasting Company (ABC)'s serial drama television series "Lost".
 The episode was written by co-creators/executive producers J. J. Abrams and Damon Lindelof, based on a story by Lindelof and directed by executive producer Jack Bender.
 The episode begins with the introduction of Juliet Burke (Elizabeth Mitchell) and The Barracks.
 The character of Jack Shephard (Matthew Fox) is featured in the episode's flashbacks.
 This is the only episode of the series other than the pilot to have been co-written by J.J. Abrams.
Elizabeth Mitchell (born Elizabeth Joanna Robertson: March 27, 1970) is an American actress known for her role as Dr. Juliet Burke on the ABC series "Lost".
 She also had lead roles on the TV series "V" and "Revolution", as well as the Snow Queen on "Once Upon a Time" and as Deb Carpenter on "Dead of Summer".
 Mitchell has starred in such films as "The Santa Clause" "2" & "", "Gia" and "".
Néstor Gastón Carbonell (] ; born December 1, 1967) is an American actor.
 He is known for his roles as Richard Alpert in ABC's drama series "Lost", and Mayor Anthony Garcia in the Christopher Nolan films "The Dark Knight" and "The Dark Knight Rises".
 He is also known for his regular roles as Luis Rivera on the sitcom "Suddenly Susan", and Batmanuel on the live-action sitcom "The Tick".
 Carbonell also portrayed Sheriff Alex Romero on A&E's drama-thriller series "Bates Motel".
The characters from the American drama/adventure television series Lost were created by Damon Lindelof and J. J. Abrams.
 The series follows the lives of plane crash survivors on a mysterious tropical island, after a commercial passenger jet from the fictional Oceanic Airlines crashes somewhere in the South Pacific.
 Each episode typically features a primary storyline on the island as well as a secondary storyline, a flashback from another point in a character's life.
The Harvard Psilocybin Project was a series of experiments in psychology conducted by Dr. Timothy Leary and Dr. Richard Alpert.
 The founding board of the project consisted of Leary, Aldous Huxley, David McClelland (Leary's superior at Harvard University), Frank Barron, Ralph Metzner, and two graduate students who were working on a project with mescaline.
 The experiments began some time in 1960 and lasted until March 1962, when other professors in the Harvard Center for Research in Personality raised concerns about the legitimacy and safety of the experiments in an internal meeting.
Hugo "Hurley" Reyes is a fictional character on the ABC television series "Lost" played by Jorge Garcia.
 For most of the show's run, Hurley served as the show's comic relief, but occasionally, and most notably in the final season, he was shown in a more serious light.
 He takes over as the Island's protector from Jack Shephard (Matthew Fox) then takes Benjamin Linus (Michael Emerson) as his adviser, the same way Jacob (Mark Pellegrino) took Richard Alpert (Nestor Carbonell).
"Not in Portland" is the 7th episode of the third season of "Lost" and the 56th episode overall.
 It first aired on February 7, 2007, on ABC.
 The episode was written by Carlton Cuse and Jeff Pinkner and was directed by Stephen Williams.
 The character of Juliet Burke (Elizabeth Mitchell) is featured in the episode’s flashbacks.
The entity referred to most frequently as The Man in Black (referred to as The Smoke Monster by the main characters) is a fictional character and the main antagonist on the American ABC television series "Lost".
 He appeared primarily as a cloud of black smoke ("The Smoke Monster") until the final episode of season five, where he appeared as a middle-aged man dressed in black.
 In season six, he primarily appeared in the physical form of John Locke.
 He exhibited the ability to "scan" the minds and memories of others, allowing him to confront characters such as Mr. Eko and Ben, with "judgment" (a replay of their pasts), and to assume the forms and memories of the deceased, starting with the original Man in Black himself, being Jacob's brother, or Christian, Yemi, Alex, and Locke.
 According to Jacob, who explains this to Richard Alpert (Nestor Carbonell), it is the incarnation of evil, and its primary goal—to escape from the island—would be the "end of everything good".
Dr. Juliet Burke (née Carlson) is a fictional character on the ABC television series "Lost" played by Elizabeth Mitchell.
 She is among the group of people referred to as the Others by the survivors of Flight 815 on the Island.
 She is a medical fertility specialist who is recruited to the Island by Richard Alpert to solve the problem of women dying during pregnancy after conceiving on the Island.
 Being unable to leave, she suffers from several breakdowns, wishing to see her sister again.
 Being unsuccessful with solving the fertility problem, she is sent as a mole to the survivors, but quickly turned on Ben, the Others, later becoming close to Jack and the remaining survivors of the crash.
 After Jack and five others are rescued, she forms a relationship with James "Sawyer" Ford.
Richard Alpert is a fictional character played by Nestor Carbonell in the American ABC television series "Lost".
 Alpert is introduced in a flashback of the character Juliet Burke (Elizabeth Mitchell), where he claims to be a doctor for a bioscience company called Mittelos Bioscience; he is later revealed to be a member of a native island faction called the Others, where he plays a role in the group's hierarchy that has been compared to that of the Panchen Lama in Buddhism by the series' producers.
 A major facet of the character is his seeming agelessness; he has been seen with a similar physical appearance both in the show's present events in the mid-2000s as well as flashbacks dating as far back as the late-1860s.
 Richard becomes mortal at the end of the series.

Question: What actress plays Juliet Burke with Richard Alpert in the television series Lost?
Answer: Elizabeth Mitchell