Following The Inside, Nichols found work on the fifth season of the serial action series Alias in 2005, being cast that July.
Nichols starred as Rachel Gibson, a computer expert who thought she was working for the CIA when in fact she was working for a dangerous criminal organization—a situation similar to that of the series' main character Sydney Bristow (Jennifer Garner) in the first season.
Discovering the truth, Gibson joins the real CIA and becomes Bristow's protégée.
Of working on Alias, Nichols said that "to say it's the nicest set on the planet is an understatement".
Her role involved multiple fight sequences, as did Garner's.
Nichols worked with Garner's personal trainer; she said she "already knew that [Garner's] job was extremely hard.
But I didn't know how difficult it was until I started training for just one fight."
Nichols was being groomed to replace Garner as the main character due to the latter's pregnancy, which had been written into the storyline.
But Alias was canceled in November 2005, making its fifth season its final. "
I think everybody knew that the show wouldn't work without Jennifer", Nichols said, "But still, they were grooming me, so it was heartbreaking when it happened."

In 2005, Nichols played a brief role in the romantic drama Shopgirl and played a more notable role as a babysitter in The Amityville Horror.
For the latter, she was nominated for the Teen Choice Award for Choice Movie Scream Scene and the MTV Movie Award for Best Frightened Performance.
She later revealed that she almost did not audition for the film due to her fear of dogs. "[
Producer] Michael Bay has these gigantic [dogs]. [...]
And, when I went to audition for The Amityville Horror, I went into his offices and literally these three huge dogs were there, and I almost turned around.
I was like, 'No, I'm not going to read for this film.'
I actually used the dogs in my audition to think of what would scare me the most."
The Amityville Horror received generally negative reception from critics, but was a commercial success.

The Woods, which had been shelved for around 18 months, was released directly-to-DVD in October 2006, to a positive critical response.
Nichols had a small part in the drama film Resurrecting the Champ (2007), playing the assistant to a sportswriter (Josh Hartnett) who believes he has found a former boxing legend (Samuel L. Jackson) living homeless on the streets.
Also that year, Nichols had a bit part in the fact-based political drama Charlie Wilson's War (2007) and was cast in a new science fiction drama television series Them, which was ultimately not picked up by Fox.

Her first starring film role was in the 2007 horror–thriller P2, as a businesswoman who becomes trapped inside a public parking garage with a deranged security guard.
About the dress her character wears for much of the film, Nichols said, "When I read the script originally, it wasn't a dress, it was a small nightgown with no bra or underwear.
Then I read the first scene where she gets wet, and I went: 'OK, this has got to be altered!'"
Nichols said in an interview that among the rules established in her contract were: "I will not get wet and show nipples" in addition to no nudity.
A bra was sewn into the "Marilyn Monroe dress" she wore in the film.
She said, "I wasn't going to run around for two months without a bra, I thought that was inappropriate.
But in place of the nipples there's clearly a lot of cleavage.
So we made a compromise."
P2 was generally disliked by critics and flopped at the box office.
Reviewer James Berardinelli said that her performance was "admirable, although one wonders whether she was cast more for her physical assets than her acting ability."
John Anderson of Variety wrote that "Nichols is in territory well trod over the years by everyone from Fay Wray and Grace Kelly to Heather Langenkamp, the terrified but gutsy heroine, who in this case has been chloroformed and put into a sheer white evening dress by her abductor—who must have anticipated that his captive would try to escape in an elevator, which he could then
Following The Inside, Nichols found work on the fifth season of the serial action series Alias in 2005, being cast that July. Nichols starred as Rachel Gibson, a computer expert who thought she was working for the CIA when in fact she was working for a dangerous criminal organization—a situation similar to that of the series' main character Sydney Bristow (Jennifer Garner) in the first season. Discovering the truth, Gibson joins the real CIA and becomes Bristow's protégée. Of working on Alias, Nichols said that "to say it's the nicest set on the planet is an understatement". Her role involved multiple fight sequences, as did Garner's. Nichols worked with Garner's personal trainer; she said she "already knew that [Garner's] job was extremely hard. But I didn't know how difficult it was until I started training for just one fight." Nichols was being groomed to replace Garner as the main character due to the latter's pregnancy, which had been written into the storyline. But Alias was canceled in November 2005, making its fifth season its final. "I think everybody knew that the show wouldn't work without Jennifer", Nichols said, "But still, they were grooming me, so it was heartbreaking when it happened."
In 2005, Nichols played a brief role in the romantic drama Shopgirl and played a more notable role as a babysitter in The Amityville Horror. For the latter, she was nominated for the Teen Choice Award for Choice Movie Scream Scene and the MTV Movie Award for Best Frightened Performance. She later revealed that she almost did not audition for the film due to her fear of dogs. "[Producer] Michael Bay has these gigantic [dogs]. [...] And, when I went to audition for The Amityville Horror, I went into his offices and literally these three huge dogs were there, and I almost turned around. I was like, 'No, I'm not going to read for this film.' I actually used the dogs in my audition to think of what would scare me the most." The Amityville Horror received generally negative reception from critics, but was a commercial success.
The Woods, which had been shelved for around 18 months, was released directly-to-DVD in October 2006, to a positive critical response. Nichols had a small part in the drama film Resurrecting the Champ (2007), playing the assistant to a sportswriter (Josh Hartnett) who believes he has found a former boxing legend (Samuel L. Jackson) living homeless on the streets. Also that year, Nichols had a bit part in the fact-based political drama Charlie Wilson's War (2007) and was cast in a new science fiction drama television series Them, which was ultimately not picked up by Fox.
Her first starring film role was in the 2007 horror–thriller P2, as a businesswoman who becomes trapped inside a public parking garage with a deranged security guard. About the dress her character wears for much of the film, Nichols said, "When I read the script originally, it wasn't a dress, it was a small nightgown with no bra or underwear. Then I read the first scene where she gets wet, and I went: 'OK, this has got to be altered!'" Nichols said in an interview that among the rules established in her contract were: "I will not get wet and show nipples" in addition to no nudity. A bra was sewn into the "Marilyn Monroe dress" she wore in the film. She said, "I wasn't going to run around for two months without a bra, I thought that was inappropriate. But in place of the nipples there's clearly a lot of cleavage. So we made a compromise." P2 was generally disliked by critics and flopped at the box office. Reviewer James Berardinelli said that her performance was "admirable, although one wonders whether she was cast more for her physical assets than her acting ability." John Anderson of Variety wrote that "Nichols is in territory well trod over the years by everyone from Fay Wray and Grace Kelly to Heather Langenkamp, the terrified but gutsy heroine, who in this case has been chloroformed and put into a sheer white evening dress by her abductor—who must have anticipated that his captive would try to escape in an elevator, which he could then 
Rachel Nichols (actress)