In the

    United States Court of Appeals
                For the Seventh Circuit
                   ____________________

No. 16-3789
KIRK HORSHAW,
                                             Plaintiff-Appellant,

                               v.

MARK CASPER, et al.,
                                          Defendants-Appellees.
                   ____________________

            Appeal from the United States District Court
                for the Southern District of Illinois.
     No. 14-CV-0248-NJR-DGW — Nancy J. Rosenstengel, Judge.
                   ____________________

 ARGUED SEPTEMBER 12, 2018 — DECIDED DECEMBER 14, 2018
                ____________________

   Before EASTERBROOK, ROVNER, and HAMILTON, Circuit
Judges.
   EASTERBROOK, Circuit Judge. On October 5, 2012, Kirk
Horshaw was brutally beaten by other inmates at Menard
Correctional Center, acting on the instructions of a gang
leader who felt himself disrespected. The injuries were
grave; Horshaw was lucky to survive and still suffers pain
and the effects of brain trauma. Horshaw had been warned
that an a_ack was in prospect; a few days (maybe weeks) be-
2                                                 No. 16-3789

fore the a_ack he received an anonymous le_er stating that
he would be “eradicated” for disrespecting the gang’s lead-
er. In this suit under 42 U.S.C. §1983 Horshaw contends that
he gave Mark Casper, a guard, a le_er describing this threat.
Horshaw asserts that Casper promised to investigate yet did
nothing. Horshaw also contends that he sent a note to Mi-
chael Atchison, then the prison’s warden, describing the
threat and asking for protection.
    The defendants concede that the a_ack occurred and that
Horshaw’s injuries are serious. But both Casper and
Atchison deny receiving these documents from Horshaw or
having any other reason to think that he was in danger. Un-
less they knew that he was at serious risk, they cannot be li-
able. See Farmer v. Brennan, 

(1994).
    The district court granted summary judgment to Casper,
Atchison, and the other two defendants, who we do not
mention because Horshaw’s appellate brief abandons his
claims against them. 

(S.D. Ill.
Sept. 27, 2016). The court found Casper not liable because,
whether or not he received the le_er, it did not establish a
specific or substantial threat. The judge wrote that the le_er,
as Horshaw remembers its contents—poorly, as he has a
brain injury and says that he gave Casper the only copy—
did not offer “any context or time frame for either his alleged
action (e.g., who he was accused of disrespecting or when it
occurred) or the threat Horshaw received. There is no evi-
dence that Horshaw identified to Casper which gang the
[warning] was talking about, who handed him the [warn-
ing], or which specific person or group he feared.” 

The court found Atchison not liable because he did not re-
ceive Horshaw’s note. 

Because the district
No. 16-3789                                                    3

judge’s ground for absolving Casper also would absolve
Atchison, even if he did receive Horshaw’s note, we start
there.
    Farmer holds that liability for failure to prevent one pris-
oner’s a_ack on another depends on proof that there was an
objectively serious threat of which the defendant was subjec-
tively aware (or to which the defendant was deliberately in-

–47. On the district court’s under-
standing, liability will be almost impossible, for prisoners do
not threaten each other with the level of detail the judge de-
manded. Agatha Christie’s A Murder Is Announced (1950) oc-
cupies a rare place in crime fiction because the murderer ad-
vertised a time and location for the crime (leading everyone
in the village to think that the announcement concerned a
game rather than an impending death). Prisoners not trying
to emulate a master storyteller omit these details—which
may be unknown to the tipster, may need to be concealed to
prevent the gang from recognizing the tipster and beating
him too, or may be unavailable (if, for example, the gang had
decided to a_ack Horshaw but not yet decided where and
when). Prisoners do not need “advance knowledge of every
detail of a future assault” to show that they faced a serious
risk. Weiss v. Cooley, 

, 1032 (7th Cir. 2000).
    Wardens and guards know that prisoners may exagger-
ate or make things up to get a_ention or benefits. A guard
who reasonably disbelieves a prisoner’s assertion is not lia-
ble just because it turns out to have been true. See, e.g., Olson
v. Morgan, 

, 713 (7th Cir. 2014); Riccardo v.
Rausch, 

, 526–28 (7th Cir. 2004). But Casper does
not contend that he deemed the threat false or hollow. He
does not say that it is the sort of thing prisoners send each
4                                                  No. 16-3789

other but do not follow up on. Casper does not contend that
Horshaw had cried “wolf” earlier and lost his credibility or
that there was some other reason to doubt that the threat
was serious. And Casper lacks the support of Warden
Atchison, who testified by deposition that, if he had received
a copy of the le_er (or even Horshaw’s note), he would have
put Horshaw in protective custody immediately. Given
these considerations, it is not possible to hold on summary
judgment that the le_er did not satisfy Farmer’s standard.
   Now for Atchison. The district court wrote that the ab-
sence of a notation in his office files showing receipt of the
note, plus his testimony that he does not remember receiving
a note from Horshaw, means that the note was not delivered
to him. Yet Horshaw testified that he wrote a note to
Atchison, put Atchison’s name on the envelope, and saw a
guard collect the note for delivery. Placing the note in the
prison mail system supports an inference of receipt. Gentry v.
Duckworth, 

, 561 (7th Cir. 1995). Cf. Hayes v. PoGer,

, 983 (7th Cir. 2002). Maybe Horshaw is lying or
unable to remember accurately what happened, or maybe
the guard who picked up the note threw it away—though
the record contains evidence that this prison’s internal-mail
system functions consistently well. But maybe Atchison saw
the note and forgot it, or maybe the staff is lying about what
the prison’s records show, or the records have been altered.
A reasonable jury could resolve this conflict either way,
which makes it inappropriate to grant summary judgment.
See Anderson v. Liberty Lobby, Inc., 

(1986).
   Atchison pitches his defense entirely on a contention that
he did not receive Horshaw’s note. He does not contend
that, as warden, he delegated to other officials the duty of
No. 16-3789                                                      5

reviewing and responding to threats. See, e.g., Miller’s Estate
v. Marberry, 

, 428 (7th Cir. 2017); Burks v. Raem-
isch, 

, 595 (7th Cir. 2009). Liability under §1983 is
direct rather than vicarious; supervisors are responsible for
their own acts but not for those of subordinates, or for failing
to ensure that subordinates carry out their tasks correctly.
See, e.g., Ashcroft v. Iqbal, 

, 676–77 (2009); Vance v.
Rumsfeld, 

, 203–05 (7th Cir. 2012) (en banc). We
held in Vance that a soldier cannot alter this rule by sending a
le_er of complaint directly to the Secretary of 

. But whether a given supervisor retained some
operational responsibilities is a question of fact. Atchison’s
testimony that he would have transferred Horshaw to pro-
tective custody had he received the note implies that he
made important operational decisions personally rather than
referring complaints to the staff. If so, he could be directly
liable under Farmer.
     One final issue requires only brief discussion. The district
court held that all defendants are entitled to qualified im-
munity, 

at *19, and defendants
ask us to accept that conclusion. But the district judge did
not find that the law is uncertain. It is not; Farmer clearly es-
tablishes the governing rules. The judge found instead that,
because the defendants are not liable at all, they also are en-
titled to immunity. That’s a confusion. Immunity is appro-
priate when the law, as applied to the facts, would have left
objectively reasonable officials in a state of uncertainty. See,
e.g., Kisela v. Hughes, 

(2018). The uncertainty
in this case is factual. Did Casper or Atchison receive some-
thing from Horshaw?; what did the le_er to Casper, or the
note to Atchison, say?; could the defendants have kept
Horshaw safe even if they tried? Atchison himself has told
6                                                 No. 16-3789

us that, if he had received a note with the contents Horshaw
describes, then he knew exactly what he was supposed to
do: offer Horshaw protection. The factual disputes may be
hard to resolve given the lapse of time and Horshaw’s brain
injury, but if he is right on the facts then neither Casper nor
Atchison is entitled to immunity. (Uncertainty about the lim-
its of supervisory liability after Iqbal and Vance might have
supported an immunity defense, but, to repeat, Atchison has
not made such an argument.)
    The district court’s judgment is vacated with respect to
Casper and Atchison and affirmed with respect to the re-
maining defendants. The case is remanded for trial.