Filling in for a speaker who can’t

The email arrives a day or two out, sometimes the morning of: a colleague’s flight got cancelled, or they’re sick, or a project back home caught fire, and the slot they were supposed to fill is still sitting in the program with their name on it. Someone has to stand in, and the ask lands on you. What you inherit in that moment is specific — an abstract already printed in the agenda, a room of people who showed up expecting a particular topic — and what you’re actually free to change is more than it feels like at first.

What the program actually promised

An abstract submitted months earlier made a promise to whoever read the program and decided this was the session worth an hour of their day: a topic, a problem, maybe a specific case. That promise is what you owe the room — not your colleague’s exact outline, not their opening story, not a tone that isn’t yours. A planned co-presented talk rehearses its handoff in advance, slide by slide; this handoff gets improvised in a day, sometimes less, and the honest move is to deliver the substance the abstract promised in whatever shape actually fits what you know and can speak to without faking it.

Say it once, plainly, and move on

The room already suspects something changed — the name at the podium doesn’t match the one printed in the agenda app, and people notice. One plain sentence near the top, something like “[Name] couldn’t make it, so I’m covering this session,” closes the question before anyone has to raise it in the Q&A instead. It costs five seconds and buys back the rest of the talk; skipping it just means the room spends the first ten minutes quietly wondering what happened instead of listening to what you’re actually saying.

A borrowed deck is a draft, not a script

If a deck exists — your colleague’s own slides, handed off in a rush — treat it as raw material, not something to read aloud. Cut the slide you can’t speak to with real confidence; a gap in the deck reads better than a gap in your own command of what’s on the screen. The usual pre-talk logistics still apply even on short notice — find the house laptop and the moderator, check the slide advance works, confirm the room’s actual setup — they just get compressed into less time than you’d like.

The invitation you didn’t ask for still deserves a real answer

Not every last-minute ask should get a yes. Declining a speaking invitation gracefully is usually about weighing an ask you had weeks to consider; this version compresses the same judgment into an hour or less — do you actually know this material well enough to stand behind it in front of this particular room, or would a short, honest no serve everyone better than a stretch you’re not ready for? Saying yes to cover a gap is generous. Saying yes to material you can’t actually deliver on isn’t generous to the audience sitting there expecting a real answer instead of a bluff.