Step One: the saddlebag

The saddlebag is on the grass at the top of the path where the knight dropped it, and the pie is on its cloth beside it with nothing in it yet but what the baker put there. In the bag: the bill from the apothecary at Arundel, five stoppered jars, a slip of paper in the vicar's hand, and a map of the brook fields. The dose goes in under the crust before the pie goes anywhere, and only one jar holds it.

The apothecary at Arundel sells by the apothecaries' weight, and prints the table at the head of every bill so that nobody can argue with him afterwards.

℈ scruple      xx grains
ʒ drachm     iij scruples
℥ ounce     viij drachms

The bill, folded small, in the saddlebag

To Sir Anselm Toller
Wolfsbane root, dry   ʒ ij
Camphor               ʒ iv
Senna, leaf           ʒ v
Rhubarb, powder       ʒ iij
Laudanum              ℥ j

Five jars, stoppered, no names. The apothecary has stamped each lid with what is in it, by weight, in scruples, because the scruple is the smallest thing he weighs and the mark on the lid is the mark on his scale.

lids:  ℈ ix    ℈ xxiv   ℈ vj
       ℈ xv    ℈ xij

The knight said the dose is in the jar marked vj.

Which of the five goes in the pie? Give its name at the lock: the first word of its line on the bill.