A secret first contact in 2390 in which the captain of the USS ibn Majid was ordered to kill two synthetic envoys, then took his own life, leaving his first officer Cristobal Rios to hide what had happened.
The ibn Majid incident is revealed in the Picard episode Broken Pieces. The ship met two visitors from an unknown world, a man called Beautiful Flower and a young woman named Jana. Captain Alonzo Vandermeer reported the contact and received a Black Flag order from Starfleet Security, issued by Commodore Oh, to kill them at once or see his ship destroyed with all hands.
Vandermeer obeyed and shot both guests. When Rios, who looked on him as a father, confronted him, the captain killed himself. Rios concealed the affair, was discharged from Starfleet after a breakdown and spent years alone on his ship La Sirena.
The truth comes out when Rios recognises Jana's face in Soji Asha. The envoys were synthetics made by Bruce Maddox and Altan Soong on Coppelius, and Oh, an agent of the Zhat Vash, had used her rank to have them destroyed.