Continuity mistake: When we see Lynette driving her kids, in the first shot we see some red, blue and white decoration in the front of the car to the right, then when the shot changes it's in the centre. (00:13:50)
Continuity mistake: When Mike comes home with the shopping bag, we see that the items in his shopping bag change positions in between the shots when he goes to see Edie arrive. (00:20:30)
Continuity mistake: When Mike is taking his dog to the vet, we see that Susan's hair is covering her ear in all the shots except the last one when her hair is behind her ear to show that the earring is gone. (00:39:30)
Answer: He was investigating the lead not the case.