Louvois led and set a very fast pace until half a mile from the finish when he gave way to Seremond who was in turn overtaken by Jack Joel's White Magic. Night Hawk, however, having been tailed-off in last place at one point, made rapid progress through the field, took the lead approaching the last quarter mile and won "easily" by two lengths from White Magic, with three lengths back to Seremond in third. The winning time of 3:03.6 was a new record for the race. William Hall Walker, who did not attend the race, was recording his first success in the St Leger, although he had bred two previous winners of the classic in Prince Palatine and Minoru. An unusual feature of the result was that while the first three home were all outsiders, the first three in the betting- Louvois, Aghdoe and Bachelor's Wedding were the last three to finish. In October Night Hawk started joint-favourite for the Cesarewitch Handicap over two and a quarter miles at Newmarket Racecourse but looked beaten a long way from home and finished unplaced behind the 50/1 winner Fiz-Yama. On 5 November Night Hawk finished last of the five runners in the Liverpool St Leger. Night Hawk ended the season with earnings of £6,450. Night Hawk remainedin training asafour-year-old but failed to win a race. At Royal Ascot in June he finished ninth of the ten runners behind the five-year-old Aleppo the Ascot Gold Cup. In late July he ran unplaced behind Collodion in the Goodwood Plate over two miles and three furlongs. In their book, "A Century of Champions", based on the Timeform rating system, John Randall and Tony Morris rated Night Hawk as the worst St Leger winner of the 20th century. At the end of his racing career Night Hawk was retired to become a breeding stallion and was subsequently exported to stand in New South Wales, Australia. Bought for 500 guineas by Reginald White of the Merton Stud, he arrived in Sydney on 25 November 1918, but by that time, White had decided to sell his stud farm. He was sold to the Martindale Stud at Muswellbrook in April 1919. Night Hawk had very little success as a sire of winners.