"Blood Will Tell" is a Nero Wolfe mystery novella by Rex Stout, first published in the December 1963 issue of Ellery Queen's Mystery Magazine. It first appeared in book form in the short-story collection Trio for Blunt Instruments, published by the Viking Press in 1964.

Archie Goodwin receives a blood-stained tie in the mail from the owner of a small walk-up apartment building in lower Manhattan, who also lives on the top floor. Archie investigates, only to find yet another dead body^[1] and now has to sort out the mess, preferably collecting a fee along the way since the other adventures in this volume have not earned the costly Nero Wolfe operation a cent.

Archie is sorting through the mails one Tuesday morning when an envelope addressed to him caught his attention. Although he usually attends to his mails after he finished with Wolfe's, that particular elegant cream coloured envelope arouses his curiosity that he feels compel to break that personal rule. The return address typed in the corner belongs to a certain James Neville Vance (which Archie has never heard of).

The envelope contains a note saying "Archie Goodwin - Keep This Until You Hear From Me - JNV" and a four-in-hand silk tie in cream coloured with thin brown diagonal stripes. He notes that there is a big brown spot near the end that he suspected as blood. Despite choosing to shrug off the whole thing, Archie can't help but waiting at home instead of going for his routine walk, in case the sender decides to call him for the next instruction.

From Lon Cohen of the Gazette, he found out that Vance is a wealthy real estate owner in his late fifties and is still a bachelor. At a quarter past eleven, a call comes from the alleged sender telling Archie to destroy the envelope and its content. The peculiarness surrounding it comples him to go to the address on the envelope to investigate, in fear that something bad has happened to the real Vance and an impersonator calls him to destroy the evidence.

Archie notices on the panel button that the four-story building is occupied by the Fougere at the bottom, Kirk in the middle, and finally James Neville Vance at the top. A conversation with Vance through the intercom reveals him to have a barritone voice rather than a squeaky one from the phone call. Vance is as perplexed as Archie and after a few exchanges, let Archie in.

Vance deny any knowledge about mailing Archie the envelope. Although he admits to own nine similar necktie, with one them is gifted to a friend and another one missing. On their way to check the stationary, the janitor and a patrol officer come to ask Vance for access to the house of one of the tenants, Mrs Kirk. The four of them go together and they discover the body of Mrs Kirk, apparently bludgeoned to death. Archie quietly slip from the scene and return to the brownstone.

He tells Nero Wolfe everything that has transpire since he left the house to which the letter express no expectation nor desire to be of service to James Neville Vance. Archie left for a walk before returning to take the envelope and its content with him before continuing to a building at 43rd street to have the stain on the necktie test for blood. The result confirms it to be human blood of less than a week old.

Archie then go to the Gazette's office to meet Lon Cohen. From Cohen and his journalists, he learns more about the deceased, Bonny Kirk. She was a former secretary in a prominent architecture firm and married architect, Martin Kirk a year ago but their marriage turned sour and he had moved out from their residence at number 219 Horn Street to stay at a hotel. Martin sought the police help to check on her wife after she didn't answer all six of his calls in eighteen hours and got no response when he rang the bell. Bonny was last seen alive by a delivery man who had delivered a bottle of vodka to her; the same bottle used by the murderer to kill her. All of the tenants in the building including the janitor is summoned by the DA office for questioning.

Archie has just arrived at the brownstone when Inspector Cramer comes and takes him back for questioning. He is detained at the DA office until after midnight.

The next day, while conversing with Wolfe about the case, the bell rang by a man Archie assumes to be a panhandler. The man turns out to be the Mr Martin Kirk and he wish to see Nero Wolfe. Wolfe reluctantly agree to meet him. Martin expresses his desire to hire Wolfe to investigate his wife's murder and clear his name. To Archie's surprise, Wolfe immediately agree and asks for a thousand dollars check as a retainer.

Wolfe insists on feeding Martin first before proceeding. Martin reveals that two months ago, Neville Vance gifted him a necktie identical to the one sent to Archie. He also reveals about his wife's infidelity with multiple men including their neighbour, Paul Fougere.

The bell rings again. This time it is Rita Fougere, Paul Fougere's wife looking for Martin. Archie let her in without consulting with Wolfe first. After asking Martin to go and check if he still has that nectie with him, he turns to question Rita. She admits to knowing about her husband's affair with Bonny but doesn't mind about it because she is in love with Martin Kirk. She also tells them about the occupants choice of alcohol; Bonny preferred gin and tonic in the summer and Bacardis in the winter, Martin favours Scotch, Vance got her husband started on Vodka, and she herself prefers sherry.

Martin calls and inform them that his necktie is missing from his belongings. He and Rita decides to visit Vance later on to ask further about the mysterious envelope. Archie vents his frustration towards Wolfe for accepting Martin as client even when the odd is against him and for not instructing him to go with Martin and Rita to meet Vance. To which Wolfe replies that he thinks Archie won't get anything useful from the meeting and that he is confident in Martin's innocence.

The meeting at Vance's turns bloody when Paul shows up unannounced and accusing Paul of killing his wife out of jealousy. After the fight subsides, Sergeant Purley Stebbins comes to take Martin for further questioning in light of new evidences. Wolfe asks Archie to use the threat of defamation lawsuit against his client as a trick to bring Paul in and it works for both the Foureges present in his office four hours later. They found out from Paul that Vance has been pinning for Bonny and that they had been intimate for some time without Martin's knowledge.

Once the couple is gone, Wolfe sits on his chair contemplating in silence for three minutes before telling Archie they're going to need Rita assistance. But it isn't urgent and can wait until after dinner. While discussing about the important points in the case, Inspector Cramer arrives. Initially Wolfe tells Archie to not let him in but changes his mind almost immediately. Cramer offers to help Wolfe persuades the district attorney to go slow on the investigation.

Wolfe asks Cramer to detain Vance for a certain period of time and explain to him his four reasoning points. Although annoyed at Wolfe's insistence to not let him in on the motive, he agrees to detain Vance at 10 o'clock tomorrow morning for six hours. Wolfe asks Archie to gather Saul, Fred, and Orrie for an operation.

The operation is to search Vance's house for the missing necktie and any incriminating clue. In order to make it a legal entry, they have Mrs Fourege to accept them from inside Vance's house, making them a legit guests in the eye of the law. Saul manages to find the necktie in a piano sheet in the studio. In about one hour before the six hour deadline, Archie found the clue they're looking for in one of the gloves in a drawer. All of them gather in Wolfe's office for the dénouement where the genius detective reveals the truth behind Bonny Kirk's murder.

• 1963, Ellery Queen's Mystery Magazine, December 1963^[2]: 78
• 1971, Ellery Queen's Anthology, Fall–Winter 1971

• 1964, New York: The Viking Press, April 24, 1964, hardcover^[2]: 86

Contents include "Kill Now—Pay Later", "Murder Is Corny" and "Blood Will Tell".

In his limited-edition pamphlet, Collecting Mystery Fiction #10, Rex Stout's Nero Wolfe Part II, Otto Penzler describes the first edition of Trio for Blunt Instruments: "Orange cloth, front cover and spine printed with blue rules; the front cover printed with blue lettering; the spine is printed with black lettering; rear cover blank. Issued in a mainly red pictorial dust wrapper."^[3]: 17

In April 2006, Firsts: The Book Collector's Magazine estimated that the first edition of Trio for Blunt Instruments had a value of between $150 and $300. The estimate is for a copy in very good to fine condition in a like dustjacket.^[4]

• 1964, New York: Viking (Mystery Guild), June 1964, hardcover

The far less valuable Viking book club edition may be distinguished from the first edition in three ways:

• The dust jacket has "Book Club Edition" printed on the inside front flap, and the price is absent (first editions may be price clipped if they were given as gifts).
• Book club editions are sometimes thinner and always taller (usually a quarter of an inch) than first editions.
• Book club editions are bound in cardboard, and first editions are bound in cloth (or have at least a cloth spine).^{[5]: 19–20}

• 1965, London: Collins Crime Club, January 1965, hardcover
• 1967, New York: Bantam #F-3298, January 1967
• 1997, New York: Bantam Crimeline ISBN 0-553-24191-5 January 1, 1997, paperback
• 1997, Newport Beach, California: Books on Tape, Inc. ISBN 0-7366-4061-4 October 31, 1997, audio cassette (unabridged, read by Michael Prichard)
• 2010, New York: Bantam Crimeline ISBN 978-0-307-75629-9 July 21, 2010, e-book

Quotations related to Blood Will Tell at Wikiquote