diff --git a/src/arboretum/dengine/node.clj b/src/arboretum/dengine/node.clj
index 3f0b5e0..19a9629 100644
--- a/src/arboretum/dengine/node.clj
+++ b/src/arboretum/dengine/node.clj
@@ -1,14 +1,13 @@
 (ns arboretum.dengine.node
   (:require
-   [arboretum.dengine.kb :refer [!kb]]
-   [arboretum.dengine.protocols :refer [Feature Node]]
-   [clojure.string :as string]))
+   [arboretum.dengine.kb :refer [!kb find-feature-for]]
+   [arboretum.dengine.protocols :refer [Feature Node]]))
 
-(defrecord NodeImpl [feature ^Boolean colour ^String fragment children]
+(defrecord NodeImpl [feature-id ^Boolean colour ^String fragment children]
   Node
   (children [this] "The children of this node" (:children this))
   (colour ^Boolean [this] "The colour of this node" (:colour this))
-  (feature [this] "The feature at this node" (:feature this))
+  (feature [this] "The feature at this node" (find-feature-for @!kb (:feature-id this)))
   (fragment ^String [this] "The explanation fragment at this node"
     (:fragment this))
   (evaluate [this case-id]
@@ -31,10 +30,17 @@
 (defn make-node 
   "Make a node. TODO: these wrapper functions will probably disappear once
    I'm more comfortable with the architecture."
-  ([feature ^Boolean colour ^String fragment]
-   (make-node feature colour fragment nil))
-  ([feature ^Boolean colour ^String fragment children ]
-  (NodeImpl. feature colour fragment children)))
+  ([feature-id ^Boolean colour ^String fragment]
+   (make-node feature-id colour fragment nil))
+  ([feature-id ^Boolean colour ^String fragment children ]
+  (if (and (find-feature-for @!kb feature-id)
+             (every? #(satisfies? Node %) children))
+    (NodeImpl. feature-id colour fragment children)
+    (throw (ex-info "Unexpected item passed as child node"
+                    {:feature-id feature-id
+                     :colour colour
+                     :fragment fragment
+                     :children children})))))
 
 ;; Here's the algorithm as published in A Graphical Inference Mechanism, 
 ;; but it's not real Interlisp code, and I remember there being at least