Each case is a plan of Ashcombe Manor laid over a square grid. A heavy line is a wall, and a gap in a wall is a doorway: an open door, which the view runs straight through. Rows are numbered from the top and columns from the left, so R2C5 is the square in the second row and the fifth column. North is at the top of the page.
Some squares hold furniture. A suspect can sit in a chair or stand on a rug, but cannot stand inside a bookcase or on top of a table. Squares nobody can stand on are dimmed and lightly hatched on the plan, and the square with the body is one of them.
Anything nobody can see past, such as a bookcase, a clock or a potted plant, has a dark outline round its whole square, like a piece of wall: a line along the square's edges, not just round the drawing. Pieces side by side share one outline. A piece without an outline never blocks the view, however big it is: you can see across a table or a bed. The Furniture, a few pages on, shows every piece in the book and says which is which.
Exactly one suspect stands in every row, and exactly one in every column. Six suspects on a six-by-six grid means no two of them share a row or a column. The body is not a suspect: its row and column still hold one suspect each.
The house and its grounds are divided into areas, each with its own name on the plan: a room indoors, a lawn or a garden outside. Areas have no such rule: an area may hold several suspects, or none. The one exception is the area with the body, which always holds exactly one (see Naming the murderer).
Every statement listed under The Clues is true. Some cases add General Clues below them, which are true of the whole house rather than of one suspect. With the rules on this page, the one about the body included, they decide where every suspect was standing. There is always exactly one answer, and you never need to guess to find it.
Once every suspect is placed, look at the area with the body. Exactly one suspect was in that area, and that suspect is the murderer. A full grid is not the end of the case: you still have to check the area. Write the name in the box under the grid, and the initial in The Ledger.
The rule works while you solve, too. If one suspect must have been in the area with the body, nobody else was there; if only one suspect still can have been there, they were.
At the top of each case, beside its tier, one to five magnifying glasses say how hard it is, judged from timed solves of cases like it. There is no clock: take as long as you like.
In the pictures, yellow squares are where the statement is true, and a red cross marks a square that is easy to count by mistake. When the answer depends on where someone stands, that suspect is marked A.
Beside. In a square next to it — up, down, left or right — and in the same area. Diagonals do not count, and neither does a square on the other side of a wall or a doorway. Sitting on something is not being beside it — not even the other end of a two-square couch or bench — but a different one next to you counts. Rugs and the ice are the exception: they count square by square, so if another square of rug or ice is next to yours, you are beside it, even while you stand on it.
In an area containing. The area holds at least one, somewhere. The suspect need not be anywhere near it: every yellow square is in an area containing a clock.
In a corner. On a square where two walls of its own area meet: one above or below it, one to its left or right. A doorway counts as wall here, and a square with a wall on one side only is not a corner. Only the heavy lines of the plan are walls: a hedge or a piece of furniture next to a square does not make it a corner.
North of, west of. Compares rows (north, south) or columns (east, west), and nothing else. Anyone in a yellow row is north of A, whatever their column.
One row south of, two columns east of. An exact distance, counted in squares from A. Someone one row south and two columns east of A can stand only on the yellow square.
When neither is placed. B was one row south and two columns east of A still rules squares out. Count the distance from each square A could take: wherever it runs off the plan, or onto a square nobody can stand on such as the table, A cannot be there. A keeps only the yellow squares, and B the same shape, one row down and two columns across.
Could see. Straight along a row or a column, through any doorway, until a wall or an outlined piece stops the view. You see the outlined piece itself, but nothing behind it. Here A sees north through the doorway into the next area, south only as far as the wall, and east as far as the outlined clock. Never diagonally, not even across an open room: A cannot see the portrait one square down and to the right. A statement about a whole room says so instead: in an area containing a portrait.
Beyond your own square. The square someone stands on does not count: sitting in an armchair, you cannot see that armchair. Wherever that could matter, the statement reminds you: Walter could not see any armchair beyond his own square. Something that covers two squares, a couch or a run of rug, is the exception: from one end you can see the other, so you can see the couch you are sitting on.
The same diagonal. Any diagonal line through both squares, not only the grid's two long ones.
Sitting on, sitting in, perched on, standing on. On the square the thing covers: sitting on the chair, sitting in the armchair, perched on the stool, on the rug. Nobody can stand on the table, so no statement ever puts anyone there.
Alone in an area, away from the body. Nobody else was in that area, and the body was not in it either. With A and the body where they are, a suspect could be alone only on a yellow square: not in A's area, and not in the body's, even though no suspect stands there.
Wore, had. What the lineup shows. Every suspect's hat, spectacles, monocle and beard are drawn in the portrait and written beneath it, as for these two. Everyone beside a bookcase, if anyone, wore a bowler keeps everyone without a bowler away from the bookcases; it does not say that anyone stood beside one. Of the people beside a clock, exactly one wore a fedora counts the fedoras among whoever stood beside any clock in the house; it does not say how many stood there.
Mark the grid in pencil with the suspects' initials. When a statement leaves a suspect a few squares, write their initial small in each; when it leaves one, write it large. The yellow squares in the practice case's pictures are where the small letters go. Every suspect's name starts with a different letter, so an initial is never ambiguous. When a suspect is placed, their whole row and column are closed to everybody else: cross out the other letters there. That one fact does more work than any clue.
The grid repeats the walls between areas, with the same doorways, hatches the squares nobody can stand on, and marks the body's square †. The furniture is only on the plan, so read the plan for what anyone was beside or could see.
Every piece in the book, drawn as on the plans. Two things matter about each one, and its card says both: whether a suspect can stand on its square, and whether a suspect can see past it. On the plans, squares nobody can stand on are also dimmed and lightly hatched, and anything nobody can see past has a dark outline round its whole square.
Some pieces look different outdoors, and those outside change with the seasons: blossom in spring, turning leaves in autumn, snow in winter. Their cards show every look side by side, above the one name, because it is the same piece wherever and whenever it stands: in every clue, a garden table is a table, and a tree in blossom is a tree.