Flight manifests obtained by the investigation show at least three members of the FSB unit flew to Kaliningrad at the same time. Security cameras at the hotel were turned off for the duration of their stay, a source has told Bellingcat.

On July 6, hours after the FSB team returned to Moscow, Yulia fell ill.

Navalny told CNN that she described a sense of sudden exhaustion and disorientation. Yulia recovered and the exact cause of her illness was not determined. Experts have told CNN that such symptoms are consistent with a low dosage of poisoning. And looking back, Navalny believes the symptoms were “absolutely the same” as those he would suffer weeks later.

“I couldn’t connect these dots. Now I realize how bad she was, what it was, the kind of terrible, terrible feeling she experienced at this time.”

After the Kaliningrad trip, the cell phone data of at least two dozen Russian officials show a surge in communications. Among those in contact were leaders of the FSB unit at the Akademika Vargi Street compound, scientific institutes and senior FSB officials.