diff --git a/src/applications/phortune/controller/PhortuneCartCheckoutController.php b/src/applications/phortune/controller/PhortuneCartCheckoutController.php
--- a/src/applications/phortune/controller/PhortuneCartCheckoutController.php
+++ b/src/applications/phortune/controller/PhortuneCartCheckoutController.php
@@ -38,6 +38,25 @@
         // This is the expected, normal state for a cart that's ready for
         // checkout.
         break;
+      case PhortuneCart::STATUS_PURCHASING:
+        // We've started the purchase workflow for this cart, but were not able
+        // to complete it. If the workflow is on an external site, this could
+        // happen because the user abandoned the workflow. Just return them to
+        // the right place so they can resume where they left off.
+        $uri = $cart->getMetadataValue('provider.checkoutURI');
+        if ($uri !== null) {
+          return id(new AphrontRedirectResponse())
+            ->setIsExternal(true)
+            ->setURI($uri);
+        }
+
+        return $this->newDialog()
+          ->setTitle(pht('Charge Failed'))
+          ->appendParagraph(
+            pht(
+              'Failed to charge this cart.'))
+          ->addCancelButton($cancel_uri);
+        break;
       case PhortuneCart::STATUS_CHARGED:
         // TODO: This is really bad (we took your money and at least partially
         // failed to fulfill your order) and should have better steps forward.
@@ -89,24 +108,8 @@
       if (!$errors) {
         $provider = $method->buildPaymentProvider();
 
-        $charge = id(new PhortuneCharge())
-          ->setAccountPHID($account->getPHID())
-          ->setCartPHID($cart->getPHID())
-          ->setAuthorPHID($viewer->getPHID())
-          ->setPaymentProviderKey($provider->getProviderKey())
-          ->setPaymentMethodPHID($method->getPHID())
-          ->setAmountAsCurrency($cart->getTotalPriceAsCurrency())
-          ->setStatus(PhortuneCharge::STATUS_PENDING);
-
-        $charge->openTransaction();
-          $charge->save();
-
-          $cart->setStatus(PhortuneCart::STATUS_PURCHASING);
-          $cart->save();
-        $charge->saveTransaction();
-
+        $charge = $cart->willApplyCharge($viewer, $provider, $method);
         $provider->applyCharge($method, $charge);
-
         $cart->didApplyCharge($charge);
 
         $done_uri = $cart->getDoneURI();
diff --git a/src/applications/phortune/provider/PhortunePaymentProvider.php b/src/applications/phortune/provider/PhortunePaymentProvider.php
--- a/src/applications/phortune/provider/PhortunePaymentProvider.php
+++ b/src/applications/phortune/provider/PhortunePaymentProvider.php
@@ -204,11 +204,13 @@
       ->setText($description)
       ->setSubtext($details);
 
+    // NOTE: We generate a local URI to make sure the form picks up CSRF tokens.
     $uri = $this->getControllerURI(
       'checkout',
       array(
         'cartID' => $cart->getID(),
-      ));
+      ),
+      $local = true);
 
     return phabricator_form(
       $user,
@@ -225,7 +227,8 @@
 
   final public function getControllerURI(
     $action,
-    array $params = array()) {
+    array $params = array(),
+    $local = false) {
 
     $digest = PhabricatorHash::digestForIndex($this->getProviderKey());
 
@@ -235,7 +238,11 @@
     $uri = new PhutilURI($path);
     $uri->setQueryParams($params);
 
-    return PhabricatorEnv::getURI((string)$uri);
+    if ($local) {
+      return $uri;
+    } else {
+      return PhabricatorEnv::getURI((string)$uri);
+    }
   }
 
   public function canRespondToControllerAction($action) {
diff --git a/src/applications/phortune/provider/PhortuneWePayPaymentProvider.php b/src/applications/phortune/provider/PhortuneWePayPaymentProvider.php
--- a/src/applications/phortune/provider/PhortuneWePayPaymentProvider.php
+++ b/src/applications/phortune/provider/PhortuneWePayPaymentProvider.php
@@ -91,8 +91,6 @@
       return new Aphront404Response();
     }
 
-    $cart_uri = '/phortune/cart/'.$cart->getID().'/';
-
     $root = dirname(phutil_get_library_root('phabricator'));
     require_once $root.'/externals/wepay/wepay.php';
 
@@ -102,6 +100,29 @@
 
     $wepay = new WePay($this->getWePayAccessToken());
 
+    $charge = id(new PhortuneChargeQuery())
+      ->setViewer($viewer)
+      ->withCartPHIDs(array($cart->getPHID()))
+      ->withStatuses(
+        array(
+          PhortuneCharge::STATUS_CHARGING,
+        ))
+      ->executeOne();
+
+    switch ($controller->getAction()) {
+      case 'checkout':
+        if ($charge) {
+          throw new Exception(pht('Cart is already charging!'));
+        }
+        break;
+      case 'charge':
+      case 'cancel':
+        if (!$charge) {
+          throw new Exception(pht('Cart is not charging yet!'));
+        }
+        break;
+    }
+
     switch ($controller->getAction()) {
       case 'checkout':
         $return_uri = $this->getControllerURI(
@@ -142,10 +163,13 @@
           'funding_sources'   => 'bank,cc'
         );
 
+        $cart->willApplyCharge($viewer, $this);
+
         $result = $wepay->request('checkout/create', $params);
 
-        // TODO: We must store "$result->checkout_id" on the Cart since the
-        // user might not end up back here. Really this needs a bunch of junk.
+        $cart->setMetadataValue('provider.checkoutURI', $result->checkout_uri);
+        $cart->setMetadataValue('wepay.checkoutID', $result->checkout_id);
+        $cart->save();
 
         $uri = new PhutilURI($result->checkout_uri);
         return id(new AphrontRedirectResponse())
@@ -175,38 +199,22 @@
                 $result->state));
         }
 
-        $currency = PhortuneCurrency::newFromString($checkout->gross, 'USD');
-
         $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
-
-          $charge = id(new PhortuneCharge())
-            ->setAmountAsCurrency($currency)
-            ->setAccountPHID($cart->getAccount()->getPHID())
-            ->setAuthorPHID($viewer->getPHID())
-            ->setPaymentProviderKey($this->getProviderKey())
-            ->setCartPHID($cart->getPHID())
-            ->setStatus(PhortuneCharge::STATUS_CHARGING)
-            ->save();
-
-          $cart->openTransaction();
-            $charge->setStatus(PhortuneCharge::STATUS_CHARGED);
-            $charge->save();
-
-            $cart->setStatus(PhortuneCart::STATUS_PURCHASED);
-            $cart->save();
-          $cart->saveTransaction();
-
+          $cart->didApplyCharge($charge);
         unset($unguarded);
 
         return id(new AphrontRedirectResponse())
-          ->setIsExternal(true)
-          ->setURI($cart_uri);
+          ->setURI($cart->getDoneURI());
       case 'cancel':
-        var_dump($_REQUEST);
+        // TODO: I don't know how it's possible to cancel out of a WePay
+        // charge workflow.
+        throw new Exception(
+          pht('How did you get here? WePay has no cancel flow in its UI...?'));
         break;
     }
 
-    throw new Exception("The rest of this isn't implemented yet.");
+    throw new Exception(
+      pht('Unsupported action "%s".', $controller->getAction()));
   }
 
 
diff --git a/src/applications/phortune/query/PhortuneChargeQuery.php b/src/applications/phortune/query/PhortuneChargeQuery.php
--- a/src/applications/phortune/query/PhortuneChargeQuery.php
+++ b/src/applications/phortune/query/PhortuneChargeQuery.php
@@ -7,6 +7,7 @@
   private $phids;
   private $accountPHIDs;
   private $cartPHIDs;
+  private $statuses;
 
   private $needCarts;
 
@@ -30,6 +31,11 @@
     return $this;
   }
 
+  public function withStatuses(array $statuses) {
+    $this->statuses = $statuses;
+    return $this;
+  }
+
   public function needCarts($need_carts) {
     $this->needCarts = $need_carts;
     return $this;
@@ -121,6 +127,13 @@
         $this->cartPHIDs);
     }
 
+    if ($this->statuses !== null) {
+      $where[] = qsprintf(
+        $conn,
+        'charge.status IN (%Ls)',
+        $this->statuses);
+    }
+
     return $this->formatWhereClause($where);
   }
 
diff --git a/src/applications/phortune/storage/PhortuneCart.php b/src/applications/phortune/storage/PhortuneCart.php
--- a/src/applications/phortune/storage/PhortuneCart.php
+++ b/src/applications/phortune/storage/PhortuneCart.php
@@ -52,17 +52,67 @@
     return $this;
   }
 
-  public function didApplyCharge(PhortuneCharge $charge) {
-    if ($this->getStatus() !== self::STATUS_PURCHASING) {
-      throw new Exception(
-        pht(
-          'Cart has wrong status ("%s") to call didApplyCharge(), expected '.
-          '"%s".',
-          $this->getStatus(),
-          self::STATUS_PURCHASING));
+  public function willApplyCharge(
+    PhabricatorUser $actor,
+    PhortunePaymentProvider $provider,
+    PhortunePaymentMethod $method = null) {
+
+    $account = $this->getAccount();
+
+    $charge = PhortuneCharge::initializeNewCharge()
+      ->setAccountPHID($account->getPHID())
+      ->setCartPHID($this->getPHID())
+      ->setAuthorPHID($actor->getPHID())
+      ->setPaymentProviderKey($provider->getProviderKey())
+      ->setAmountAsCurrency($this->getTotalPriceAsCurrency());
+
+    if ($method) {
+      $charge->setPaymentMethodPHID($method->getPHID());
     }
 
-    $this->setStatus(self::STATUS_CHARGED)->save();
+    $this->openTransaction();
+      $this->beginReadLocking();
+
+      $copy = clone $this;
+      $copy->reload();
+
+      if ($copy->getStatus() !== self::STATUS_READY) {
+        throw new Exception(
+          pht(
+            'Cart has wrong status ("%s") to call willApplyCharge(), expected '.
+            '"%s".',
+            $copy->getStatus(),
+            self::STATUS_READY));
+      }
+
+      $charge->save();
+      $this->setStatus(PhortuneCart::STATUS_PURCHASING)->save();
+    $this->saveTransaction();
+
+    return $charge;
+  }
+
+  public function didApplyCharge(PhortuneCharge $charge) {
+    $charge->setStatus(PhortuneCharge::STATUS_CHARGED);
+
+    $this->openTransaction();
+      $this->beginReadLocking();
+
+      $copy = clone $this;
+      $copy->reload();
+
+      if ($copy->getStatus() !== self::STATUS_PURCHASING) {
+        throw new Exception(
+          pht(
+            'Cart has wrong status ("%s") to call didApplyCharge(), expected '.
+            '"%s".',
+            $copy->getStatus(),
+            self::STATUS_PURCHASING));
+      }
+
+      $charge->save();
+      $this->setStatus(self::STATUS_CHARGED)->save();
+    $this->saveTransaction();
 
     foreach ($this->purchases as $purchase) {
       $purchase->getProduct()->didPurchaseProduct($purchase);
diff --git a/src/applications/phortune/storage/PhortuneCharge.php b/src/applications/phortune/storage/PhortuneCharge.php
--- a/src/applications/phortune/storage/PhortuneCharge.php
+++ b/src/applications/phortune/storage/PhortuneCharge.php
@@ -9,8 +9,6 @@
 final class PhortuneCharge extends PhortuneDAO
   implements PhabricatorPolicyInterface {
 
-  const STATUS_PENDING    = 'charge:pending';
-  const STATUS_AUTHORIZED = 'charge:authorized';
   const STATUS_CHARGING   = 'charge:charging';
   const STATUS_CHARGED    = 'charge:charged';
   const STATUS_FAILED     = 'charge:failed';
@@ -27,6 +25,11 @@
   private $account = self::ATTACHABLE;
   private $cart = self::ATTACHABLE;
 
+  public static function initializeNewCharge() {
+    return id(new PhortuneCharge())
+      ->setStatus(self::STATUS_CHARGING);
+  }
+
   public function getConfiguration() {
     return array(
       self::CONFIG_AUX_PHID => true,