Afoot

on foot; walking:
i came afoot.
astir; in progress:
there is mischief afoot.
contemporary examples

police suspected a serial killer was afoot and dubbed him the southside slayer.
la’s grisly woman killer christine pelisek october 26, 2011

a few facts (or perhaps “facts”) were given about each illness, but hardly enough to know if anything of concern was afoot.
bob dole & george h.w. bush hospitalized: how to interpret illness of public figures kent sepkowitz november 29, 2012

the same impulse is afoot in less trendy parts of the country.
ban e-cigarettes? the anti-smoking lobby’s clueless crusade nick gillespie august 24, 2013

even the world heath organization, which has plenty to worry about in impoverished nations, knows there is big trouble afoot.
new study says doctors can’t “just say no” to their patients kent sepkowitz march 30, 2014

those interested in post palace intrigue, though, wondered if something else was afoot with the announcement.
new york post looks thinner after news corporation split david freedlander july 17, 2013

historical examples

that put me afoot, and climbing up and down them hills i lost my bearings and didn’t know where i was at for a day or two.
the happy family bertha muzzy bower

one side was in the saddle and determined; the other afoot and grimly desperate.
the escape of mr. trimm irvin s. cobb

the giants had now become so interested in whatever plan they had afoot, that they paid little attention to the ship.
five thousand miles underground roy rockwood

it is the time, too, when all sorts of travelling people are afoot.
the friendly road (aka david grayson) ray stannard baker

the old race-course was surrounded by thousands upon thousands of people in carriages, on horseback, and afoot.
little n-body mrs. alex. mcveigh miller

adjective, adverb (postpositive)
in circulation or operation; astir: mischief was afoot
on or by foot
adj.

c.1200, afote, from a- “on” (see a- (1)) + foot (n.). figurative sense of “in active operation” is from 1601 (“julius caesar”).