diff --git a/plugins/themes/themes.plugin.zsh b/plugins/themes/themes.plugin.zsh
index 7a2a00fea..9c1b47fcf 100644
--- a/plugins/themes/themes.plugin.zsh
+++ b/plugins/themes/themes.plugin.zsh
@@ -1,24 +1,55 @@
-function theme
-{
-  if [ -z "$1" ] || [ "$1" = "random" ]; then
-    themes=($ZSH/themes/*zsh-theme)
-    N=${#themes[@]}
-    ((N=(RANDOM%N)+1))
-    RANDOM_THEME=${themes[$N]}
-    source "$RANDOM_THEME"
-    echo "[oh-my-zsh] Random theme '$RANDOM_THEME' loaded..."
+# Load a theme
+# 
+# Usage:
+#   "theme <name>" loads the named theme
+#   "theme random" or "theme" with no argument loads a random theme
+# Return value:
+#   0 on success
+#   Nonzero on failure, such as requested theme not being found
+function theme() {
+  if [[ -z "$1" ]] || [[ "$1" = "random" ]]; then
+    # Select a random theme
+    local themes n random_theme
+    themes=($(lstheme))
+    n=${#themes[@]}
+    ((n=(RANDOM%n)+1))
+    random_theme=${themes[$n]}
+    echo "[oh-my-zsh] Loading random theme '$random_theme'..."
+    theme $random_theme
   else
-    if [ -f "$ZSH_CUSTOM/$1.zsh-theme" ]
-    then
-      source "$ZSH_CUSTOM/$1.zsh-theme"
-    else
-      source "$ZSH/themes/$1.zsh-theme"
+    # Main case: load named theme
+    local name theme_dir found
+    name=$1
+    found=false
+    for theme_dir ($ZSH_CUSTOM $ZSH_CUSTOM/themes $ZSH/themes); do
+      if [[ -f "$theme_dir/$name.zsh-theme" ]]; then
+        source "$theme_dir/$name.zsh-theme"
+        found=true
+        break
+      fi
+    done
+    if [[ $found == false ]]; then
+      echo "[oh-my-zsh] Theme not found: $name"
+      return 1
     fi
   fi
 }
 
-function lstheme
-{
-  cd $ZSH/themes
-  ls *zsh-theme | sed 's,\.zsh-theme$,,'
+# List available themes by name
+#
+# The list will always be in sorted order, so you can index in to it.
+function lstheme(){
+  local themes x theme_dir
+  themes=()
+  for theme_dir ($ZSH_CUSTOM $ZSH_CUSTOM/themes $ZSH/themes); do
+    if [[ -d $theme_dir ]]; then
+      themes+=($(_omz_lstheme_dir $theme_dir))
+    fi
+  done
+  echo ${(F)themes} | sort | uniq
 }
+
+# List themes defined in a given dir
+function _omz_lstheme_dir() {
+  ls $1 | grep '.zsh-theme$' | sed 's,\.zsh-theme$,,'
+}
\ No newline at end of file