Denis O'Hare OBVIOUSLY Did It!!!
When Father Chris Shea (Denis O'Hare) is attacked in his car, vigilantes assume the assailant is the homeless-looking black guy in the vicinity and beat him up, after which said black guy gets arrested.
Fin (Ice-T) intervenes, because the presumed attacker, Sam Randall (Eric LaRay Harvey), is Fin's ex-wife's brother, whereupon he finds out that Sam stopped two other guys who were beating up Fr. Shea and calling him "short eyes." Sofia (Nicolette Pierini), the little girl who was in the priest's car when he was first attacked, corroborates Sam's story.
The priest's real attackers, Adam (Victor Cruz) and Enrique (Theo Rossi) were beating him up to avenge Enrique's sister; Enrique believes the priest raped Enrique's sister Angelica (Gizel Jimenez) when she was thirteen, got her pregnant, and made her get an abortion. But! Enrique got the wrong guy; it was a senior priest at the parish who, because he knew Fr. Shea had been in a consensual relationship with the parish secretary (Melissa Marsala) and got her pregnant with Sofia, used this knowledge to have Fr. Shea transferred to another parish.
Way too many molesting priests to mention, though a female victim of childbearing age is somewhat unusual.
Though the casting of frequent Law & Order perp Denis O'Hare does predispose the audience to think he's guilty, the real culprit is Fr. Menendez, who's played by Tony Plana -- also a repeat L&O guest, but best known these days as Ugly Betty's dad.
Fr. Menendez "said it happened because [Angelica] was evil, that she seduced him....He said he was going to make her do it until she didn't want it again, to exorcise the demon of sex in her."
Fin and Rollins (Kelli Giddish) labour mightily to get the charges against Sam dropped, even though there's no "Good Samaritan" exception when it comes to beating people up, and he is on parole. And the judge (Peter Gerety) agrees, because it's Christmas.
Obviously Fin, but Amaro (Danny Pino) as well, since he's the father of a girl roughly Sofia's age whom he doesn't live with full-time, and because he's a Catholic who feels the need to defend the Church from his colleague's prejudice, which...you know, turns out to be well-founded.
The judge asks Amaro to wait until after Fr. Menendez finishes saying Christmas Eve mass before arresting him -- which just gives Angelica enough time to bust into the church and shoot Fr. Menendez, apparently fatally. So: n/a.
Benson (Mariska Hargitay) is spending the holidays in the Caribbean with a man, of whom we see nothing but his hand. (Presumably it's Harry Connick Jr.'s David Hadden, and producers just didn't feel like paying him for the episode, but maybe it isn't!) (Probably it is.)