diff --git a/luprex/core/cpp/invocation.cpp b/luprex/core/cpp/invocation.cpp
index c79ffb4d..efba1c7e 100644
--- a/luprex/core/cpp/invocation.cpp
+++ b/luprex/core/cpp/invocation.cpp
@@ -1,6 +1,15 @@
 
 #include "invocation.hpp"
 
+const std::string &InvocationData::get(const std::string &key) const {
+    static std::string blank_;
+    auto iter = find(key);
+    if (iter == end()) {
+        return blank_;
+    } else {
+        return iter->second;
+    }
+}
 
 void InvocationData::serialize(StreamBuffer *sb) const {
     assert(int(size()) < 65536);
diff --git a/luprex/core/cpp/invocation.hpp b/luprex/core/cpp/invocation.hpp
index c05908e8..3c728327 100644
--- a/luprex/core/cpp/invocation.hpp
+++ b/luprex/core/cpp/invocation.hpp
@@ -9,6 +9,8 @@
 
 class InvocationData : public std::map<std::string, std::string> {
 public:
+    const std::string &get(const std::string &key) const;
+    
     void serialize(StreamBuffer *sb) const;
     void deserialize(StreamBuffer *sb);
 };
@@ -18,6 +20,7 @@ public:
     enum Kind {
         KIND_INVALID,
         KIND_PLAN,
+        KIND_LUA,
     };
 
 private:
diff --git a/luprex/core/cpp/textgame.cpp b/luprex/core/cpp/textgame.cpp
index 4ffdd438..263ac1df 100644
--- a/luprex/core/cpp/textgame.cpp
+++ b/luprex/core/cpp/textgame.cpp
@@ -47,60 +47,6 @@ public:
 
 
 
-static lua_State *globalL = NULL;
-
-
-static void lstop(lua_State *L, lua_Debug *ar)
-{
-    (void)ar; /* unused arg. */
-    lua_sethook(L, NULL, 0, 0);
-    /* Avoid luaL_error -- a C hook doesn't add an extra frame. */
-    luaL_where(L, 0);
-    lua_pushfstring(L, "%sinterrupted!", lua_tostring(L, -1));
-    lua_error(L);
-}
-
-static void laction(int i)
-{
-    signal(i, SIG_DFL); /* if another SIGINT happens before lstop,
-			 terminate process (default action) */
-    lua_sethook(globalL, lstop, LUA_MASKCALL | LUA_MASKRET | LUA_MASKCOUNT, 1);
-}
-
-static void l_message(const char *msg)
-{
-    fputs(msg, stderr);
-    fputc('\n', stderr);
-    fflush(stderr);
-}
-
-void TextGame::do_lua(const std::string &exp) {
-    assert(world_->stack_is_clear());
-    lua_State *L = world_->state();
-    // push the compiled function.
-    int status = luaL_loadbuffer(L, exp.c_str(), exp.size(), "=stdin");
-    assert(status == LUA_OK);
-    globalL = L;
-    signal(SIGINT, laction);
-    status = traceback_pcall(L, 0, LUA_MULTRET);
-    signal(SIGINT, SIG_DFL);
-    if (status == LUA_OK) {
-        if (lua_gettop(L) > 0) {
-            lfn_pprint_pprint(L);
-            lua_settop(L, 0);
-        }
-    } else {
-        const char *msg = lua_tostring(L, -1);
-        if (msg == NULL) {
-            msg = "(error object is not a string)";
-        }
-        l_message(msg);
-        lua_pop(L, 1);
-        lua_gc(L, LUA_GCCOLLECT, 0);
-    }
-    assert(world_->stack_is_clear());
-}
-
 void TextGame::do_view_command(const StringVec &cmd) {
     if (cmd.size() != 1) {
         std::cerr << "v command (view) takes no arguments" << std::endl;
@@ -154,6 +100,13 @@ void TextGame::do_choose_command(const StringVec &cmd) {
     world_->invoke(inv);
 }
 
+void TextGame::do_lua(const std::string &exp) {
+    assert(world_->stack_is_clear());
+    InvocationData dummyresult;
+    Invocation inv(Invocation::KIND_LUA, actor_id_, actor_id_, exp, dummyresult);
+    world_->invoke(inv);
+}
+
 void TextGame::do_snapshot_command(const StringVec &cmd) {
     if (cmd.size() != 1) {
         std::cerr << "s command (snapshot) takes no arguments" << std::endl;
diff --git a/luprex/core/cpp/world-core.cpp b/luprex/core/cpp/world-core.cpp
index 12c50c02..b2c5d266 100644
--- a/luprex/core/cpp/world-core.cpp
+++ b/luprex/core/cpp/world-core.cpp
@@ -4,6 +4,7 @@
 #include "animqueue.hpp"
 #include "gui.hpp"
 #include "traceback.hpp"
+#include "print.hpp"
 #include <iostream>
 
 void World::store_global_pointer(lua_State *L, World *v) {
@@ -320,11 +321,21 @@ void World::update_gui(int64_t actor_id, int64_t place_id, Gui *gui) {
     assert(stack_is_clear());
 }
 
+void World::update_source(util::LuaSourcePtr source) {
+    if (source != nullptr) {
+        source_db_.update(*source);
+        source_db_.rebuild(true);
+    }
+}
+
 void World::invoke(const Invocation &inv) {
     switch (inv.kind()) {
     case Invocation::KIND_PLAN:
         invoke_plan(inv.actor(), inv.place(), inv.action(), inv.data());
         break;
+    case Invocation::KIND_LUA:
+        invoke_lua(inv.actor(), inv.place(), inv.action(), inv.data());
+        break;
     default:
         // Do nothing.  Standard behavior for any invalid command is to
         // simply do nothing at all.  Perhaps eventually we may add a flag
@@ -335,14 +346,56 @@ void World::invoke(const Invocation &inv) {
     }
 }
 
-void World::update_source(util::LuaSourcePtr source) {
-    if (source != nullptr) {
-        source_db_.update(*source);
-        source_db_.rebuild(true);
+void World::invoke_lua(int64_t actor_id, int64_t place_id, const std::string &action, const InvocationData &data) {
+    assert(stack_is_clear());
+
+    // Get the actor and place, which must be the same.
+    if (actor_id != place_id) return;
+    Tangible *tactor = tangible_get(actor_id);
+    if (tactor == nullptr) {
+        return;
     }
+
+    lua_State *L = state();
+    LuaVar closure;
+    LuaStack LS(L, closure);
+
+    // create the compiled closure.
+    int status = luaL_loadbuffer(L, action.c_str(), action.size(), "=invoke");
+    lua_replace(L, closure.index());
+    if (status != LUA_OK) {
+        // The closure is actually an error message. Do nothing.
+        LS.result();
+        return;
+    }
+
+    // Call the closure.
+    int top = lua_gettop(L);
+    lua_pushvalue(L, closure.index());
+    set_lthread_state(actor_id, place_id, false);
+    status = traceback_pcall(L, 0, LUA_MULTRET);
+    set_lthread_state(0, 0, false);
+
+    // If there's an error message, print it.
+    // Otherwise, pretty-print the results.
+    if (status == LUA_OK) {
+        for (int i = top + 1; i <= lua_gettop(L); i++) {
+            LuaSpecial root(i);
+            pprint(LS, root, true, &std::cout);
+            std::cout << std::endl;
+        }
+    } else {
+        const char *msg = lua_tostring(L, top);
+        if (msg == NULL) {
+            msg = "(error object is not a string)";
+        }
+        std::cerr << msg << std::endl;
+    }
+    LS.result();
+    assert(stack_is_clear());
 }
 
-void World::invoke_plan(int64_t actor_id, int64_t place_id, const std::string &action, const InvocationData &idata) {
+void World::invoke_plan(int64_t actor_id, int64_t place_id, const std::string &action, const InvocationData &data) {
     assert(stack_is_clear());
 
     // Validate that the action is legal.
@@ -401,7 +454,7 @@ void World::invoke_plan(int64_t actor_id, int64_t place_id, const std::string &a
 
     // Convert the InvocationData into a lua table.
     LS.newtable(invdata);
-    for (const auto &p : idata) {
+    for (const auto &p : data) {
         LS.rawset(invdata, p.first, p.second);
     }
 
diff --git a/luprex/core/cpp/world.hpp b/luprex/core/cpp/world.hpp
index 520136b2..9eb4d9f7 100644
--- a/luprex/core/cpp/world.hpp
+++ b/luprex/core/cpp/world.hpp
@@ -173,7 +173,7 @@ public:
     // To mutate a world model, create an invocation, then invoke it.
     //
     void invoke(const Invocation &inv);
-
+    
     // Update the source database from disk.
     //
     // Special case: if the source pointer is nullptr, does not update.
@@ -240,8 +240,12 @@ private:
 
     // Invoke a plan.
     //
-    void invoke_plan(int64_t actor_id, int64_t place_id, const std::string &action, const InvocationData &idata);  
+    void invoke_plan(int64_t actor_id, int64_t place_id, const std::string &action, const InvocationData &data);
 
+    // Invoke a lua string.
+    //
+    void invoke_lua(int64_t actor_id, int64_t place_id, const std::string &action, const InvocationData &data);
+    
 public:
     ////////////////////////////////////////////////////////////////////////////
     //