While Commander Koenig is away on an exploratory mission, a Croton ship, broadcasting the Universal Plague Warning Signal gains (with difficulty) permission to land on Alpha. On arrival, Sahala, the female ship captain(?), attacks Maya with a staser, explaining it is because Maya is a Psychon, and a ship of Psychons caused considerable tormoil among Sahala's people. Sahala is confined. Tony does not want to hear any explanation from Sahala, but Alan is willing to give her a chance, and prompts her to bring Maya out of stasis. On board the Croton ship is Dorzak, the primary Psychon instigator, according to Sahala. Maya indicates Dorzak is a philosopher and a poet, and pleads with Tony to speak to him, desperate to talk to someone of her race again. Sahala claims insideous powers from Dorzak; and upon his being brought out of stasis, he uses telepathic projection to force another Croton, Yesta, to give false witness against Sahala, who ends up imprisoned again. Alan still believes Sahala, and even Tony starts having doubts about Dorzak, and finally convinces a very reluctant Maya to transform herself into Sahala's form, to hear Dorzak's own words. She does, and finds the ugly truth about yet another Psychon, and wonders if Psychon nature is flawed. Dorzak, not practiced in metamorphosis, forces his way into her mind to gain the secrets, forces her to molecularly transform into his appearance, and transforms into hers, a metamorphic masquerade of which Tony eventually becomes suspicious. Tony confronts Dorzak and stuns him. The Croton ship, with Dorzak safely back in stasis, leaves, after Alan and Sahala share a kiss goodbye.

Details

Clea fell in love with Dorzak, and her freeing him is what precipitated the crisis on board the Croton ship that brought it to Alpha: though Sahala regains control over her ship, it is not before Clea gives Yesta a head injury, and Clea herself, in remorse, throws herself into space. These circumstances are what prompt Sahala to seek help from Alpha.
Crotons developed a defense against Dorzak's "organic psycho waves," in the form of a small brain implant: a Neuro-Pulsonic Jammer. Tony finds one sitting free on the Croton ship (Clea's?), and sends it to Technical Section for analysis, not knowing what it is. Helena removes one from Yesta's brain, also not knowing what it is. Tony talks to Sam (?) from Technical, and they work out what it might be, which is part of what makes Tony more suspicious of Dorzak. After becoming suspicious of Dorzak's masquerade as Maya, but before confronting Dorzak, Tony has Dr. Spencer(?) implant one in his brain, so Tony can be immune to Dorzak.

Comments

The Universal Plague Warning Signal is presumably known to the Alphans via some post-Breakaway source, such as deciphering some part of the Voyager 1 records, from Maya, or from another alien source.