My friend David Cramer has a brief review of Gone Baby Gone posted at CBHD. In the review he points out that the film serves as a case study on ethical theory.
One is constantly torn between an appeal for “doing the right thing” and an appeal for “showing compassion.” This movie does not provide easy answers, but rather forces the viewer to choose between two ethical paradigms— absolutist and consequentialist—and to witness the ramifications of that decision.