Never use an adverb to modify the verb 'said' . . . he admonished gravely. To use an adverb this way (or almost any way) is a mortal sin. The writer is now exposing himself in earnest, using a word that distracts and can interrupt the rhythm of the exchange.
Elmore LeonardAvoid prologues: they can be ยญannoying, especially a prologue ยญfollowing an introduction that comes after a foreword.
Elmore Leonard