Iain Campbell has begun noting the interactions of the players in the novels as it refers to how they relate to each other in the unspoken Code that they live by. It's covered in bits and pieces and deserves some serious study but here's the article so far.
This book (Chance) might have as a sub-title Debts among subscribers to the Code. Last page, Ch 31, Spenser has to apologize to Vinnie for suggesting that he might betray to them the secrets of Gino Fish, the man whose money he accepts. (Curious that Bernard J. Fortunato can sell Bibi to both Spenser and Marty - and still get invited along for the Potshot picnic. Must be a nuance I am missing.)
(Actually it works for me. Spenser and Marty were both former clients so each deserved repeat service. And since Marty had stiffed him last time I assume Bernard made him pay for past and present information and only then told him where Bibi was. -Bob)
Note that at the final shoot-out, the fat Mexican who clearly is not a Code-carrying mensch, walks out on Marty in his hour of need, even though he has presumably pocketed his cash.
Last page, Ch.39, Spenser can't ask Belson for help lest he think that Spenser is calling in the debt incurred in "Thin Air" so Quirk watches the wires instead. Susan spots the delicacy among tough guys and comments.
Ch.45, Joe Broz helps Spenser out, but then, being a bad guy who merely knows the Code rather than being a Code-carrying believer/member of the Hard-Boiled Club, asks Spenser "We even now?". Spenser had of course never even hinted that there existed a state of not-even-ness, that Joe owed him, and points this out to Joe, who is forced to recognize this tact. How crass! Really!
Rumination 2: On Small VicesEdit
Note Belson states that he owes Spenser one, and insists on being on the special detail. OK for him to say, not for Spenser. Note that Gino Fish comes up with Rugar information, perhaps gratuitously, perhaps because of the way Spenser handled things in Chance.
Note that Rugar accepts Stapleton's money (since the contract was apparently successfully completed), yet turns him in on a technicality i.e. that he had no agreement covering failure. (Did he give Stapleton a refund, I wonder? If he didn't, I would think that he still owes him Spenser's demise.) I don't think Vinnie would have done this (See his objections to Spenser's questioning in Chance). But Rugar is just a stone killer, not a Believer in the Code.