Answer:
Mr. H. knew the printer would help them upon release from prison.
Step-by-step explanation:
It can be inferred from the passage that Mr. H. intervened to release the printer from prison for a reason that probably had nothing to do with sympathy and everything to do with personal interests.
To have been able to find the jailed printer in the first place, Mr. H. would have had to know where to look. If he were looking then he was probably looking for something or someone and the printer was the man he needed to owe him a favor.