Nell (Renée Felice Smith) will take the lead in the team's next mission to flush out the mole in the upcoming episode of "NCIS: Los Angeles."

In the episode titled "Sirens," the synopsis (as per CarterMatt) reveals that new details will surface about the spy hiding in the NCIS ranks. It has been a while since the squad got a lead regarding the culprit. His/her capture means Hetty (Linda Hunt) will get to keep her position in the organization. Previously, she had to beg the Secretary of the Navy to let her return to the squad to personally lead the team in tracking down the mole. The clock is ticking fast, though. The mole is still one step ahead of them, evading capture until now.

The day will start with a double murder in front of Callen's (Chris O'Donnell) apartment. Two men pretending to be cops will be found killed by an unknown female assailant. Later on, Nell will be sent in prison to interview someone suspected to know more information about the spy. Unfortunately, the inmate does not wish to share material with NCIS. Nell will have to use her best interrogation skills to make him spill his secrets.

Nell has been doing a good job as Kensi's (Daniela Ruah) substitute on the team. Deeks (Eric Christian Olsen) has no problem working with her. They all want Kensi to recover fast from her injuries from the Syrian mission. Last episode, she could already walk. It was a huge step, considering she was in therapy for only two months. Still, Kensi was frustrated that she could not get well as fast as she expected. Deeks has been very patient with her through her ordeal. He frequently reminds her that there are four more months of therapy she has to undergo.

"NCIS: Los Angeles" airs Sundays at 8 p.m. EST on CBS.