The 23-year-old woman is being evaluated at a nearby hospital "where she appears to be in good health," Boston Police Department Commissioner William Gross told reporters at a news conference.
A 38-year-old Charlestown man identified by police as Victor Pena was arrested and charged with kidnapping on Tuesday after she was found inside his apartment, Gross said.
“When we made entry she was observed standing in the apartment near the suspect," the police commissioner said. "We eventually separated them and the suspect was apprehended."
She was last seen around 11 p.m. Saturday leaving Hennessy's bar, where she was with her twin sister and friends. Police said she left with a man who was later determined not to be connected to her disappearance.
Around 11:40 p.m., she was spotted on surveillance video with "two unknown males." One of them walked ahead of her while the other "place[d] his arm around" her, police said, and later identified as Pena.
Surveillance video from around 12 a.m. showed her "being accompanied by that same male, still with his arm around her," leaving a train station in Charlestown. At 12:13 a.m., she and the man were spotted walking, and soon after, the woman's phone was recorded as being in a nearby housing development.
Her family in a statement released Tuesday night said they're "grateful" for those who assisted in the search to find the 23-year-old, and thanked Boston Police, Massachusetts Bay Transportation Authority and Transit police, as well as Hennessy's bar for their help.