diff --git a/mod/greeting.cpp b/mod/greeting.cpp
new file mode 100644
index 0000000..a8101b8
--- /dev/null
+++ b/mod/greeting.cpp
@@ -0,0 +1,13 @@
+#include "greeting.hpp"
+
+#include <sstream>
+
+namespace greeting {
+
+std::string make_greeting(std::string const& greetee) {
+  std::ostringstream out;
+  out << "Hello " << greetee << "!";
+  return out.str();
+}
+
+}
diff --git a/mod/greeting.hpp b/mod/greeting.hpp
new file mode 100644
index 0000000..c9d1a3d
--- /dev/null
+++ b/mod/greeting.hpp
@@ -0,0 +1,9 @@
+#pragma once
+
+#include <string>
+
+namespace greeting {
+
+std::string make_greeting(std::string const& greetee);
+
+}