A rare and incurable disease that was killing Rukiya, the young daughter of Doctor Joseph M'Benga, who hid her in the Enterprise's medical transporter buffer to halt its progress.
Cygnokemia is a fatal illness for which 23rd-century Federation medicine has no cure. Doctor M'Benga's daughter Rukiya was diagnosed with it as a small child, with only weeks left to live.
Strange New Worlds reveals his response in Ghosts of Illyria. M'Benga keeps Rukiya's pattern suspended in the buffer of the sickbay's emergency medical transporter, where she does not age and the disease cannot advance, and materialises her now and then for a bedtime story so that the pattern does not degrade. Una Chin-Riley discovers the secret and helps him protect it.
The story ends in The Elysian Kingdom. A lonely consciousness living in the Jonisian Nebula transforms the ship into the fairy tale Rukiya loves, and offers to let her live on within it, free of her body and her illness. M'Benga lets her go, and she returns moments later to him as a grown woman to say farewell.