While a mystery man (later identified as Sheila's lawncare worker Juan) took Noah while the boy was shopping with Sheila, it turned out that Sheila orchestrated the entire ordeal.
Sheila initially played along with the kidnapping story, but as she got a second away from Olivia, she bolted and met up with the kidnapper to run off with Noah. She apparently had a plan to cross the border with him using fake passports.
Noah repeatedly asks where his mom is, but Sheila lies and tells him Olivia knows all about their plans. She even pretends to call and leave a message for Olivia to ease Noah's worries.
The SVU team followed leads provided by Sheila's attorney and private investigator to get them to Juan. From there, Juan leads them to what turns out to be a dead end. Sheila had orchestrated multiple false leads in the event of a pursuit.
However, Olivia follows her own lead and ends up confronting Sheila in a remote cabin. Sheila pulls a gun on Olivia, and the two face off.
Ultimately, Noah interrupts the altercation, and Olivia subdues Sheila. Sheila is then arrested.
Law & Order: Special Victims Unit airs Wednesdays at 9 p.m. ET on NBC.