The covert transfer of a village of pre-warp Boraalans to a new world by Worf's foster brother Nikolai Rozhenko, in defiance of the Prime Directive, as their planet's atmosphere collapsed.
In The Next Generation episode Homeward, the Enterprise-D answers a call from Nikolai Rozhenko, a Federation observer on Boraal II, whose atmosphere is about to dissipate. Picard rules that the Prime Directive forbids intervention, and the crew watch the planet die.
Nikolai has already acted. He has beamed the villagers he lived among into a holodeck copy of their caves, and presents Picard with the result. The only course left is to carry the deception through: the holodeck is slowly altered to simulate a long journey while the ship finds a suitable planet, Vacca VI, and Worf goes along in disguise.
The holodeck keeps failing, and the village chronicler Vorin wanders out into the ship. Unable to go back with what he knows or to live among strangers, he takes his own life. The others are settled safely. Nikolai stays with them and with Dobara, who is carrying his child.