The Plot Thickens $20.00 Inside Message Blank Inside Packages of Heartstrings® cards are shrink-wrapped and sold in sets of 10 cards with envelopes. The actual card size is 4 1/4" x 5 1/2". The Plot Thickens quantity Add to cart SKU: 131. Categories: Baby - Parenting, Gardening, Hearts. Related Products A Big Addition $20.00 We Grow Together $20.00 Flowers Chase the Blues $20.00 Sweet Thanks $20.00