One night, John wakes Beauty up in the middle of the night and saddles him up as fast as he can. Squire Gordon tells John to ride for his life—"that is, for your mistress's life" (18.3). This doesn't sound good. John and Beauty ride out to fetch Doctor White at Squire Gordon's request.
When they reach a long, flat stretch of road, John urges Beauty on, saying, "Now, Beauty, do your best" (18.6). Beauty doesn't need to be told twice, and gallops "as fast as I could lay my feet to the ground. I don't believe my old grandfather, who won the race at Newmarket, could have gone faster" (18.6). Well then. They race the eight miles to town and seek out Doctor White. John tells Doctor White that Mrs. Gordon might die without help.
Doctor White says that his own horse is badly in need of rest, and John tells him to take Beauty back, even though he's just run all the way there: "Black Beauty will go till he drops" (18.14), John says.
Even though the doctor is heavier and not a great rider, Beauty does his best, taking him back to Squire Gordon's as fast as he can. Once back at the stable, Beauty is wiped out—he's drenched, steaming, and shaking with the effort of making the run. Little Joe tries to take care of him, but has no experience, and doesn't know to put a warm cloth on Beauty's back to prevent a chill.
Unfortunately Joe's inexperience proves to be a problem. Beauty begins to "shake and tremble […] My legs ached my loins ached, and my chest ached, and I felt sore all over" (18.16). Uh-oh…
When John finally arrives after a long while, Beauty actually moans in pain. John fixes Beauty up with warm cloths and food, and seems very upset that Joe didn't properly care for Beauty.
Even more unfortunately, Beauty gets very sick because of his post-run chill, but John cares for him, even getting up during the night to tend to the horse. Squire Gordon also visits, telling Beauty that he saved the mistress's life.
John tells Squire Gordon that it seemed like Beauty knew what was happening that night, to which Beauty tells us, "Of course I did" (18.18). We believe you, Beauty.