Liverpool west

I have gf sailing on 4/4/1873 with the Agent Allan Brothers. Would he "always" have had to follow with Allan to Quebec? I have already ordered microfilm for New York arrivals since there are 5 ships with not much waiting time in Liverpool and if not on there will order microfilm for Quebec. Allan Ship would have had him wait for about 10 days before leaving Liverpool. If Quebec, was there a standard connection to continue through the lakes. His older sister I've been told also went to Quebec and then to Detroit Michigan. Thanks for any help Judy