i could have used this 30 years ago...

eleventh-hour.ts

const alphabet = Array.from('abcdefghijklmnopqrstuvwxyz')
const codedMessage = Array.from(`
    myxqbkdevkdsyxc!

    sd gkc sxnoon usvbyi dro wyeco gry cdyvo dro pokcd. led ro rkn rovz:
    yxo rexnbon kxn ovofox yp usvbyi'c pebbi bovkdsfoc rsn drowcovfoc sx
    dro ryeco kxn kbyexn dro qkbnox kxn, kd ovofox wsxedoc dy ovofox droi
    kvv cmkwzobon sxdy dro lkxaeod rkvv gsdr usvbyi kxn kdo ez kvv yp
    rybkmo'c lokedspev pyyn.

    kxn xyg, tecd dy cryg ryg mvofob iye kbo, mkx iye psxn yxo rexnbon
    kxn ovofox wsmo rsnnox sx dro zsmdeboc?

    rkzzi rexdsxq!
`)

const shiftAlphabet = (amount: number) =>
  Array.from(alphabet.slice(amount).concat(alphabet.slice(0, amount)))

const decodeMessage = (suspect: string) => {
  const firstInitial = suspect.charAt(0).toLowerCase()
  const shift = alphabet.length - alphabet.indexOf(firstInitial)
  const shiftedAlphabet = shiftAlphabet(shift)

  return codedMessage
    .map((char) => {
      const pos = alphabet.indexOf(char)
      if (pos > -1) return shiftedAlphabet[pos]
      return char
    })
    .join('')
}

console.log(decodeMessage('Maxwell'))