diff --git a/assets/styles/app.css b/assets/styles/app.css
index bdeb0dd..f505d64 100644
--- a/assets/styles/app.css
+++ b/assets/styles/app.css
@@ -429,6 +429,23 @@ table.dataTable {
 }
 .storyline-pager-title { font-weight: 600; }
 
+/* Chapter notes: collapsible card above the chapter body */
+.storyline-notes > summary {
+    cursor: pointer;
+    list-style: none;
+    font-weight: 600;
+}
+.storyline-notes > summary::-webkit-details-marker { display: none; }
+.storyline-notes > summary::before {
+    content: "\25B8";              /* right-pointing triangle */
+    display: inline-block;
+    margin-right: 0.5rem;
+    color: var(--bs-secondary-color);
+    transition: transform 0.15s ease;
+}
+.storyline-notes[open] > summary::before { transform: rotate(90deg); }
+.storyline-notes textarea { font-size: 0.95rem; line-height: 1.6; }
+
 /* Chapter list: kicker line above each title */
 .storyline-chapter-kicker {
     display: block;
diff --git a/migrations/Version20260908164955.php b/migrations/Version20260908164955.php
new file mode 100644
index 0000000..ec7b676
--- /dev/null
+++ b/migrations/Version20260908164955.php
@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+/**
+ * Auto-generated Migration: Please modify to your needs!
+ */
+final class Version20260908164955 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return "Add chapter_note table for the DM's per-chapter storyline notes";
+    }
+
+    public function up(Schema $schema): void
+    {
+        // ENGINE = InnoDB is pinned explicitly: the local WAMP MariaDB defaults
+        // to MyISAM, which would silently drop the unique index behaviour.
+        $this->addSql('CREATE TABLE chapter_note (id INT AUTO_INCREMENT NOT NULL, slug VARCHAR(120) NOT NULL, notes LONGTEXT DEFAULT NULL, updated_at DATETIME DEFAULT NULL, UNIQUE INDEX uniq_chapter_note_slug (slug), PRIMARY KEY (id)) DEFAULT CHARACTER SET utf8mb4 ENGINE = InnoDB');
+    }
+
+    public function down(Schema $schema): void
+    {
+        $this->addSql('DROP TABLE chapter_note');
+    }
+}
diff --git a/src/Controller/StorylineController.php b/src/Controller/StorylineController.php
index 2c01f11..2448a9c 100644
--- a/src/Controller/StorylineController.php
+++ b/src/Controller/StorylineController.php
@@ -2,7 +2,11 @@
 
 namespace App\Controller;
 
+use App\Form\ChapterNoteType;
+use App\Repository\ChapterNoteRepository;
+use Doctrine\ORM\EntityManagerInterface;
 use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
+use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\Routing\Attribute\Route;
 use Symfony\Component\Security\Http\Attribute\IsGranted;
@@ -46,13 +50,27 @@ class StorylineController extends AbstractController
         ]);
     }
 
-    #[Route('/storyline/{slug}', name: 'app_storyline_chapter', requirements: ['slug' => '[a-z0-9-]+'], methods: ['GET'])]
-    public function chapter(string $slug): Response
+    #[Route('/storyline/{slug}', name: 'app_storyline_chapter', requirements: ['slug' => '[a-z0-9-]+'], methods: ['GET', 'POST'])]
+    public function chapter(string $slug, Request $request, ChapterNoteRepository $notes, EntityManagerInterface $em): Response
     {
         if (!isset(self::CHAPTERS[$slug])) {
             throw $this->createNotFoundException('No such storyline chapter.');
         }
 
+        $note = $notes->findOrCreate($slug);
+        $form = $this->createForm(ChapterNoteType::class, $note);
+        $form->handleRequest($request);
+
+        if ($form->isSubmitted() && $form->isValid()) {
+            if (null === $note->getId()) {
+                $em->persist($note);
+            }
+            $em->flush();
+            $this->addFlash('success', 'Chapter notes saved.');
+
+            return $this->redirectToRoute('app_storyline_chapter', ['slug' => $slug]);
+        }
+
         $slugs = array_keys(self::CHAPTERS);
         $pos = array_search($slug, $slugs, true);
 
@@ -60,6 +78,8 @@ class StorylineController extends AbstractController
             'chapters' => self::CHAPTERS,
             'slug' => $slug,
             'chapter' => self::CHAPTERS[$slug],
+            'note' => $note,
+            'form' => $form,
             'prev' => $pos > 0 ? $slugs[$pos - 1] : null,
             'next' => $pos < \count($slugs) - 1 ? $slugs[$pos + 1] : null,
         ]);
diff --git a/src/Entity/ChapterNote.php b/src/Entity/ChapterNote.php
new file mode 100644
index 0000000..dfe7876
--- /dev/null
+++ b/src/Entity/ChapterNote.php
@@ -0,0 +1,72 @@
+<?php
+
+namespace App\Entity;
+
+use App\Repository\ChapterNoteRepository;
+use Doctrine\DBAL\Types\Types;
+use Doctrine\ORM\Mapping as ORM;
+
+/**
+ * The DM's running notes for one storyline chapter. Chapters themselves are
+ * hand-written Twig (see StorylineController::CHAPTERS); this table only holds
+ * the mutable play notes, keyed by the chapter slug.
+ */
+#[ORM\Entity(repositoryClass: ChapterNoteRepository::class)]
+#[ORM\Table(name: 'chapter_note')]
+#[ORM\UniqueConstraint(name: 'uniq_chapter_note_slug', columns: ['slug'])]
+#[ORM\HasLifecycleCallbacks]
+class ChapterNote
+{
+    #[ORM\Id]
+    #[ORM\GeneratedValue]
+    #[ORM\Column]
+    private ?int $id = null;
+
+    #[ORM\Column(length: 120)]
+    private string $slug;
+
+    #[ORM\Column(type: Types::TEXT, nullable: true)]
+    private ?string $notes = null;
+
+    #[ORM\Column(type: Types::DATETIME_IMMUTABLE, nullable: true)]
+    private ?\DateTimeImmutable $updatedAt = null;
+
+    public function __construct(string $slug)
+    {
+        $this->slug = $slug;
+    }
+
+    #[ORM\PrePersist]
+    #[ORM\PreUpdate]
+    public function touch(): void
+    {
+        $this->updatedAt = new \DateTimeImmutable();
+    }
+
+    public function getId(): ?int
+    {
+        return $this->id;
+    }
+
+    public function getSlug(): string
+    {
+        return $this->slug;
+    }
+
+    public function getNotes(): ?string
+    {
+        return $this->notes;
+    }
+
+    public function setNotes(?string $notes): static
+    {
+        $this->notes = $notes;
+
+        return $this;
+    }
+
+    public function getUpdatedAt(): ?\DateTimeImmutable
+    {
+        return $this->updatedAt;
+    }
+}
diff --git a/src/Form/ChapterNoteType.php b/src/Form/ChapterNoteType.php
new file mode 100644
index 0000000..bfd7236
--- /dev/null
+++ b/src/Form/ChapterNoteType.php
@@ -0,0 +1,32 @@
+<?php
+
+namespace App\Form;
+
+use App\Entity\ChapterNote;
+use Symfony\Component\Form\AbstractType;
+use Symfony\Component\Form\Extension\Core\Type\TextareaType;
+use Symfony\Component\Form\FormBuilderInterface;
+use Symfony\Component\OptionsResolver\OptionsResolver;
+
+/**
+ * The DM's running log for a storyline chapter.
+ */
+class ChapterNoteType extends AbstractType
+{
+    public function buildForm(FormBuilderInterface $builder, array $options): void
+    {
+        $builder->add('notes', TextareaType::class, [
+            'required' => false,
+            'label' => false,
+            'attr' => [
+                'rows' => 12,
+                'placeholder' => "What happened at the table: the story the party told about the cottage, names they gave NPCs, promises made, threads to pick up next time…",
+            ],
+        ]);
+    }
+
+    public function configureOptions(OptionsResolver $resolver): void
+    {
+        $resolver->setDefaults(['data_class' => ChapterNote::class]);
+    }
+}
diff --git a/src/Repository/ChapterNoteRepository.php b/src/Repository/ChapterNoteRepository.php
new file mode 100644
index 0000000..4af0b69
--- /dev/null
+++ b/src/Repository/ChapterNoteRepository.php
@@ -0,0 +1,27 @@
+<?php
+
+namespace App\Repository;
+
+use App\Entity\ChapterNote;
+use Doctrine\Bundle\DoctrineBundle\Repository\ServiceEntityRepository;
+use Doctrine\Persistence\ManagerRegistry;
+
+/**
+ * @extends ServiceEntityRepository<ChapterNote>
+ */
+class ChapterNoteRepository extends ServiceEntityRepository
+{
+    public function __construct(ManagerRegistry $registry)
+    {
+        parent::__construct($registry, ChapterNote::class);
+    }
+
+    /**
+     * The note row for a chapter, or a fresh unsaved one. The caller persists
+     * it only if something is actually written.
+     */
+    public function findOrCreate(string $slug): ChapterNote
+    {
+        return $this->findOneBy(['slug' => $slug]) ?? new ChapterNote($slug);
+    }
+}
diff --git a/templates/storyline/chapter.html.twig b/templates/storyline/chapter.html.twig
index c99afb4..f522e9c 100644
--- a/templates/storyline/chapter.html.twig
+++ b/templates/storyline/chapter.html.twig
@@ -22,6 +22,24 @@
         </nav>
 
         <div class="col-lg-9 order-lg-1">
+            <details class="card shadow-sm mb-4 storyline-notes" open>
+                <summary class="card-header d-flex justify-content-between align-items-center">
+                    <span>📝 Chapter notes</span>
+                    {% if note.updatedAt %}
+                        <span class="text-body-secondary small fw-normal">saved {{ note.updatedAt|date('Y-m-d H:i') }}</span>
+                    {% endif %}
+                </summary>
+                <div class="card-body">
+                    <p class="text-body-secondary small mb-2">
+                        Your running log for this chapter — what actually happened at the table.
+                    </p>
+                    {{ form_start(form) }}
+                    {{ form_row(form.notes) }}
+                    <button class="btn btn-primary mt-2">Save notes</button>
+                    {{ form_end(form) }}
+                </div>
+            </details>
+
             <article class="storyline-doc">
                 <header class="storyline-doc-head">
                     <div class="storyline-eyebrow">Storyline &middot; {{ chapter.eyebrow }}</div>
diff --git a/tests/Entity/ChapterNoteTest.php b/tests/Entity/ChapterNoteTest.php
new file mode 100644
index 0000000..928aaad
--- /dev/null
+++ b/tests/Entity/ChapterNoteTest.php
@@ -0,0 +1,38 @@
+<?php
+
+namespace App\Tests\Entity;
+
+use App\Entity\ChapterNote;
+use PHPUnit\Framework\TestCase;
+
+class ChapterNoteTest extends TestCase
+{
+    public function testStartsEmptyForItsSlug(): void
+    {
+        $note = new ChapterNote('prologue-the-long-road');
+
+        self::assertSame('prologue-the-long-road', $note->getSlug());
+        self::assertNull($note->getId());
+        self::assertNull($note->getNotes());
+        self::assertNull($note->getUpdatedAt());
+    }
+
+    public function testTouchStampsUpdatedAt(): void
+    {
+        $note = new ChapterNote('overview');
+        $note->setNotes("The party told Maud the cottage was haunted.");
+        $note->touch();
+
+        self::assertNotNull($note->getUpdatedAt());
+        self::assertSame("The party told Maud the cottage was haunted.", $note->getNotes());
+    }
+
+    public function testNotesCanBeClearedBackToNull(): void
+    {
+        $note = (new ChapterNote('overview'))->setNotes('something');
+
+        $note->setNotes(null);
+
+        self::assertNull($note->getNotes());
+    }
+}