The story takes place in the far future. Human travel in outer space is threatened by strange creatures known as the Dragons. Imperceptible to ordinary people, Dragons are experienced as nothing but a sudden death or insanity. Dragons can only be destroyed by very strong light, but they move too fast for conventional defense methods. Both human and telepathic cats (who perceive the dragons as rats) are able to sense the creatures within milliseconds. The humans and cats work together as teams to protect interstellar spaceships traveling via planoforming (a type of faster than light speed travel). The cats ride outside of the spaceships in their own tiny crafts, waiting for the order from their human partner to attack. Pin-sets (telepathic amplifiers) heighten a telepathâs senses and allow the humans to communicate with their partner cats. The cats then destroy the Dragons with "pinlights", miniature nuclear bombs whose blast gives off pure visible radiance that can destroy the dragons. Thanks to the combination of the human mind and the cats' quick reactions, the battle against the Dragons is not only possible, but usually ends in victory.
Underhill, Woodley, Father Moontree, and a girl named West are the group of current telepaths fighting the war. The cats fighting alongside them are Captain Wow, Lady May and others. Woodley draws an unremarkable cat, West teams up with Captain Wow, Underhill with Lady May, and Father Moontree gets stuck with an old, unnamed, greedy male cat, who has the best fighting record of them all. While the Father Moontree and Woodley are not particularly interested in their partner cats, West thinks Captain Wow is cuddly, and Underhill has a strong connection with Lady May and enjoys being telepathically connected with her.
The team travel to the depths of space, searching for their enemy. During an attack, Underhill is unable to follow Lady Mayâs thoughts fast enough and the Dragon touches his mind, sending excruciating pain throughout his body. The battle lasts less than the blink of an eye, and the ship lands safely. Underhill is hospitalized and a doctor tells him that he was within a tenth of a millisecond of going insane, but the only thing that concerns Underhill is his partner, Lady May, and her well-being. A secretly jealous and angry nurse walks in and Underhill compares her to Lady May. Logically, he understands that Lady May is only a cat, but his mind tells him that no woman will ever equal her.

Question: Why does Underhill start feeling pain?
Answer: Because he can't follow his cat's thoughts fast enough, so the Dragon touches his mind.
Alternative answer: A dragon touches his mind