With its third-to-last episode ever, CBS’ NCIS: Los Angeles this Sunday night made headway in answering Callen’s lingering questions about his childhood as a Drona subject.

This week’s episode saw Callen get invited to a meet-up with Harold Pembrook (played again by Jere Burns), though the elusive and infamous Drona shrink went to great pains to make sure that he and Grisha were alone and not surveilled. To that end, he led Callen into a swimming pool… a change of clothes… and then a van (inside of which Pembrook was crouched with a pistol). Pembrook then directed Callen to drive them to a parking garage some miles away.

There, Pembrook detailed how Beltran and several other Drona subjects — scattered among many forms of law enforcement and government agencies — are gunning for him, seeking revenge for his cruel programming of them as children. Pembrook repeatedly expressed remorse, to Grisha, for what he had done. In fact, when their current ordeal is over, he promised to give Grisha all of the papers from his Drona file.

Their huddle was cut short by the arrival of Beltran and other Drona alumni, guns a-blazing. Callen and Pembrook managed to slip away via a fire stairwell, though the latter got winged in the shoulder by a bullet. With Beltran & Co. in pursuit, Callen and Pembrook ascended several floors, eventually hunkering down in a server closet that had a bolted, steel door. The baddies drilled through the lock only to find a supine, bleeding Pembrook on the floor. When Pembrook said that he and Callen split up, two baddies left to find Callen. We then saw that Callen was perched inside above the door, from where he shot one Drona guy, and then dropped down to shoot another. Kensi and Rountree arrived in time to corral the rest.

Alas, before Pembrook could elaborate on one of the bombs hells he dropped on Callen — that Hetty had removed Grisha from the Drona program as soon as she realized what Pembrook was up to — he was carted away by CIA officer/Drona alum Baer. But later, Callen got a call from Pembrook, asking to meet him outside HQ. There, Pembrook turned over the hefty file on Grisha, rife with details on his lineage and more. As for Callen’s big question — why did Hetty never tell him that she pulled him from Drona? — Pembrook explained that Henrietta always felt remorse for her role in his indoctrination. She simply saw an opportunity for a gifted child to reach his full potential, as any parent would.

When Callen challenged that, Pembrook made clear that Grisha, more than anyone else ever, was to Hetty the son she never had. And Pembrook knows this because A) he himself has been “watching” over Grisha for 35 years, and 2) he has at times been a sounding board for Ms. Henrietta Lange.

Then, with a nod to the file in Callen’s hands, Pembrook advised, “Don’t make your life being just about the past. Let it be about the present, and now the future” — alluding to G’s engagement. “I wish you all the happiness in the world,” he professed. “I really do.”

Before walking away, Pembrook noted that inside the file can be found the dossier on Sam Hanna that he forwarded to Hetty some years ago.

“I thought he’d make a great partner. No, that’s not true. I thought he’d make a great friend,” Pembrook explained. “In spite of everything, I tried to look out for you. I tried to make up for it all.”

NCIS: LA‘s two-part “New Beginnings” series finale kicks off next Sunday, May 14, and concludes Sunday, May 21 at a special time, 9/8c (followed by a retrospective special).