Centurion Alexios Flavius Aquila, nephew of the Dux Britanniarum (Roman Governor of Northern Britain) and therefore, at 23, second in command of a fort, becomes first when the commander is killed in a raid by native tribes. Against standing orders and the advice of an older and wiser subordinate, Alexios panics and orders a retreat that proves disastrous. In disgrace, then, he is sent to command a Northern outpost of Frontier Wolves, most recruited from neighboring tribes and together a close-knit, rough, and independent unit with its own determined ways. Alexios, though, has learned to heed the comments of his officers and the moods and customs of his men--and so, in strong, expertly modulated scenes, he gains their respect, obtains his own wolf cloak as the others have, and wins the friendship of Cunorix, eldest son of the local chieftain and soon chieftain himself. The trouble comes a year after Alexios' arrival, when an insensitive new Praepositus (regional commander) arrives for an inspection tour. His beautiful horse is stolen "half in jest" by Cunorix's impetuous brother Connla, and the Praepositus has Connla executed in retaliation. Thus it is that, when invading tribes attack the fort next morning, Cunorix's local tribesmen are among them. This time, it takes "almost more courage than [Alexios] possessed" to order evacuation, and as much endurance to shepherd the men to safety, wounded and all, through much battling and one inevitably tragic man-to-man contest between Alexios and his friend Cunorix. As always, Sutcliff brings the frontier society of "wolves" and tribesmen to powerful, three-dimensional life and makes their trials and decisions matter urgently.