diff --git a/CHANGELOG.md b/CHANGELOG.md
index aa1faf9..df3954e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -28,6 +28,10 @@ the current version is `interlock.__version__` (mirrored into `VERSION` by
 ### Added
 - `interlock.LeaseNotIssued`, a subclass of `InterlockError`, plus `LeaseManager.issued()`
   and `LeaseManager.is_revoked()`.
+- 90-second demonstrator (`scripts/demo_90s.py`, transcript in `demo/TRANSCRIPT.md`): a narrated
+  end-to-end run of grant, keepalive, permit, expiry denial, resource-scoped fault gate,
+  global e-stop, provenance-stamped claim, and ledger audit. Exits non-zero on any unexpected
+  behavior.
 
 ## [0.1.0] — 2026-09-27
 ### Added
diff --git a/README.md b/README.md
index e366cf5..ec9bc55 100644
--- a/README.md
+++ b/README.md
@@ -57,6 +57,8 @@ claim = ilk.claim(
 
 The fastest path to a first lease is [`docs/guides/quickstart.md`](docs/guides/quickstart.md).
 
+**90-second demonstrator:** `python3 scripts/demo_90s.py` runs the substrate end to end, narrated: grant, keepalive, permit, expiry denial, resource-scoped fault gate, global e-stop, provenance-stamped claim, and ledger audit. It exits non-zero if any step misbehaves. Expected output: [`demo/TRANSCRIPT.md`](demo/TRANSCRIPT.md).
+
 ## How it fails
 
 | Condition | Behavior |
diff --git a/demo/README.md b/demo/README.md
new file mode 100644
index 0000000..94e43ec
--- /dev/null
+++ b/demo/README.md
@@ -0,0 +1,23 @@
+# The 90-second demonstrator
+
+`scripts/demo_90s.py` runs Interlock end-to-end in one terminal, narrated:
+
+1. **GRANT** — authority comes into existence only here, and it expires.
+2. **KEEPALIVE** — renewal moves the expiry; it cannot resurrect a dead lease.
+3. **PERMIT** — the gate passes: e-stop clear, lease live, no gating fault.
+4. **EXPIRED** — a lapsed lease is denied, and the denial is on the record.
+5. **FAULT** — a gating fault refuses permits on its resource only (`web:read`
+   gated, `docs:write` unaffected).
+6. **E-STOP** — one engagement halts every permit; release is explicit.
+7. **CLAIM** — the run is stamped as a provenance-bearing claim.
+8. **AUDIT** — the ledger holds every permit and every denial.
+
+The expected output is captured in [TRANSCRIPT.md](TRANSCRIPT.md); the script
+exits non-zero if any step behaves unexpectedly, so the transcript doubles as
+a smoke test.
+
+Run it:
+
+```bash
+python3 scripts/demo_90s.py
+```
diff --git a/demo/TRANSCRIPT.md b/demo/TRANSCRIPT.md
new file mode 100644
index 0000000..761d9cc
--- /dev/null
+++ b/demo/TRANSCRIPT.md
@@ -0,0 +1,12 @@
+[01] GRANT — authority comes into existence only here, and it expires.
+[02]        lease 8da9a55b030c4424af6f25f633e05157 → docs:write · holder research-agent · ttl 30s
+[03] KEEPALIVE — renewal moved the expiry (moved=True). It cannot resurrect a dead lease.
+[04] PERMIT — gate passed: e-stop clear, lease live, no gating fault. brief.md written.
+[05] EXPIRED — the lapsed lease is denied. The denial is on the record.
+[06] FAULT — TOOL_TIMEOUT gates web:read. Faults are resource-scoped: docs:write is unaffected.
+[07] PERMIT — docs:write still flows while web:read is gated.
+[08] E-STOP — one engagement halts every permit, everywhere.
+[09] RELEASE — explicit release only. Permits flow again.
+[10] CLAIM — provenance-stamped [inferred]: Demo run: 3 permits granted, 3 denied (expiry, fault, e-stop).
+[11] AUDIT — ledger holds 3 permits, 3 denials, 1 claim. Nothing happened off the record.
+[12]        denial reasons on record: estop, fault, lease_expired
diff --git a/scripts/demo_90s.py b/scripts/demo_90s.py
new file mode 100644
index 0000000..603385a
--- /dev/null
+++ b/scripts/demo_90s.py
@@ -0,0 +1,107 @@
+#!/usr/bin/env python3
+"""Interlock 90-second demonstrator.
+
+A narrated end-to-end run of the substrate, in one terminal:
+
+  GRANT      authority comes into existence only here, and it expires
+  KEEPALIVE  renewal moves the expiry; it cannot resurrect a dead lease
+  PERMIT     the gate passes: e-stop clear, lease live, no gating fault
+  EXPIRED    a lapsed lease is denied
+  FAULT      a gating fault refuses permits on its resource only
+  E-STOP     one engagement halts every permit; release is explicit
+  CLAIM      the run is stamped as a provenance-bearing claim
+  AUDIT      the ledger holds every permit and every denial
+
+Run:  python3 scripts/demo_90s.py
+"""
+
+from __future__ import annotations
+
+import sys
+import time
+
+sys.path.insert(0, "src")
+
+from interlock import EStopEngaged, FaultActive, Interlock, LeaseExpired  # noqa: E402
+
+_step = 0
+
+
+def say(text: str) -> None:
+    global _step
+    _step += 1
+    print(f"[{_step:02d}] {text}", flush=True)
+
+
+def main() -> int:
+    ilk = Interlock()
+
+    say("GRANT — authority comes into existence only here, and it expires.")
+    lease = ilk.grant(resource="docs:write", holder="research-agent", ttl_seconds=30)
+    say(f"       lease {lease.id} → docs:write · holder research-agent · ttl 30s")
+
+    old_expiry = lease.expires_at
+    ilk.leases.keepalive(lease)
+    moved = lease.expires_at > old_expiry
+    say(f"KEEPALIVE — renewal moved the expiry ({moved=}). It cannot resurrect a dead lease.")
+
+    with ilk.permit(lease, action="write", target="brief.md"):
+        say("PERMIT — gate passed: e-stop clear, lease live, no gating fault. brief.md written.")
+
+    short = ilk.grant(resource="docs:write", holder="research-agent", ttl_seconds=1)
+    time.sleep(1.2)
+    try:
+        with ilk.permit(short, action="write", target="late.md"):
+            pass
+        say("EXPIRED — UNEXPECTED: lapsed lease was permitted")
+        return 1
+    except LeaseExpired:
+        say("EXPIRED — the lapsed lease is denied. The denial is on the record.")
+
+    web = ilk.grant(resource="web:read", holder="research-agent", ttl_seconds=300)
+    ilk.faults.report(code="TOOL_TIMEOUT", severity="major", resource="web:read")
+    try:
+        with ilk.permit(web, action="fetch", target="https://example.com/feed"):
+            pass
+        say("FAULT — UNEXPECTED: gated resource was permitted")
+        return 1
+    except FaultActive:
+        say("FAULT — TOOL_TIMEOUT gates web:read. Faults are resource-scoped: docs:write is unaffected.")
+    with ilk.permit(lease, action="write", target="brief-v2.md"):
+        say("PERMIT — docs:write still flows while web:read is gated.")
+
+    ilk.estop.engage(reason="operator review requested")
+    try:
+        with ilk.permit(lease, action="write", target="brief-v3.md"):
+            pass
+        say("E-STOP — UNEXPECTED: permit passed under e-stop")
+        return 1
+    except EStopEngaged:
+        say("E-STOP — one engagement halts every permit, everywhere.")
+    ilk.estop.release()
+    with ilk.permit(lease, action="write", target="brief-v3.md"):
+        say("RELEASE — explicit release only. Permits flow again.")
+
+    claim = ilk.claim(
+        text="Demo run: 3 permits granted, 3 denied (expiry, fault, e-stop).",
+        provenance="demo:scripts/demo_90s.py",
+        authority=lease.id,
+        review_after_days=7,
+        falsifier="re-run scripts/demo_90s.py and compare the transcript",
+    )
+    say(f"CLAIM — provenance-stamped [{claim.status}]: {claim.text}")
+
+    permits = list(ilk.ledger.read_series("permits"))
+    denials = list(ilk.ledger.read_series("denials"))
+    claims = list(ilk.ledger.read_series("claims"))
+    say(
+        f"AUDIT — ledger holds {len(permits)} permits, {len(denials)} denials, "
+        f"{len(claims)} claim. Nothing happened off the record."
+    )
+    reasons = sorted({d.get("reason") for d in denials})
+    say(f"       denial reasons on record: {', '.join(reasons)}")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())