■ TWO SHALLOW GRAVES: “THE DESERT PING” & “WHERE’S DAN?”

Investigation Discovery, beginning at 9 p.m.; also streams on discovery+ Two new hourlong installments of this true-crime docuseries are available today, beginning with “The Desert Ping,” in which Merritt’s phone pings near the desert graves, and authorities wonder whether he buried the bodies or merely visited a sister. Then, “Where’s Dan?” looks into how new DNA evidence found in the graves may reveal who murdered the Mcstays.