CREATE TABLE table_58943 ("Tie no" TEXT, "Home team" TEXT, "Score" TEXT, "Away team" TEXT, "Attendance" TEXT)

Who was the away team that played Northampton Town at home with a tie number of replay?
SELECT "Away team" FROM table_58943 WHERE "Tie no" = 'replay' AND "Home team" = 'northampton town'
SELECT "Away team" FROM "table_58943" WHERE "Home team" = 'northampton town' AND "Tie no" = 'replay'