Catherine tells Maxine about a crime scene that disappeared five years ago involving Rafael Tarquenio.

Max still isn't sold on Allie's plan for permanent partners.

Josh is scheduled to be interrogated by Internal Affairs tomorrow.

Catherine and Beau go back to the boat where the body disappeared five years ago.

Catherine locates a prosthetic leg.

Chris and Penny have to determine how to clean algae off the leg.

They find a serial number on the leg. It belonged to Theresa Moren, a dean at a prep school that Tarquenio's daughter attends.

Moren supposedly died in a scuba accident in Mexico five years ago.

The CSIs attempt to determine what substance caused damage to the leg.

Nora Cross is handling Folsom's inquiry. She breaks off their first session quickly, planning to reconvene tomorrow at the hangar where they interrogated Schefter.

A lab tech intimates to Catherine that Tarquenio's donations are all that's keepng his daughter from being expelled.

Catherine and Allie collect chromic acid samples from lumber at Tarquenio's building sites.

Then Allie scampers off for a clandestine meeting with Josh.

Nora has asked her to join the questioning tomorrow. Folsom is concerned because he thought he saw a note in Serena's handwriting in Cross' file.

Blood has been found in the school's science lab and Dean Canto is missing. There's a gold watch among the ashes in the kiln, just like the one Canto was wearing earlier.

A security guard recalled an argument between Moren and Tarquenio.

Nora hands Allie a photo of Jeannette with blood on it to be run for DNA.

Maxine tells Catherine she's concerned that Catherine is too obsessed about Tarquenio.

They determine there were two sources of blood in the lab which Penny and Chris examine.

Allie grills Serena about her connection to Nora. She discovers Serena has been doing oversight on the crime lab since coming on board. Not even Josh knows.

Chris and Penny determine Canto wasn't the body in the kiln. Catherine and Max figure out the body was covered in tattoos, and turns out to be one of the painters on the gym renovation project.

Allie finds out Max knew about Serena's role.

The blood on the photo was Jeannette's.

They found a stabbed Canto in a supply room.

Canto had been helping Tarquenio launder his drug money through the gym renovations.

He says that Tarquenio killed Moren himself and wants witness protection.

Catherine says he's an accomplice, for mixing up the chromic acid.

Canto added that Tarquenio hurt himself and still had a scar from the injury. 

Bone from Moren was recovered from that scar.

Serena confesses to Josh about her role with IA. They break up.