The investigators first met Joseph Hall in New York in early 1925, where he was a partner in Darrow and Hall, Private Investigations. His partner, Simon Darrow, had recently been murdered by the Cult of the Bloody Tongue, and business was suffering.
To add to his troubles Joe was in debt to the Macettis, for a very large amount, and when Jack Macetti realised that Joe couldn't keep up the payments, thing turned rather nasty. Joe promptly left town and headed to Boston, hoping to lie low and perhaps get a job with AAK. At the time he arrived, Chuck and Steel were out of the country investigating the missing Carlyle Expedition. However Mrs Adamcyk spotted an opportunity and promptly employed him (on an informal basis).
This arrangement was formalised when Chuck and the Steels returned to Boston in June 1925, and Joe is now a valuable member of the team. Pen has also paid off Joe's debt to the Macettis (though Joe isn't aware of this).