no direct bus or train.
take train from malgrat to blanes then bus to lloret then bus to tossa.
there are also tourist boats that go up the coast, but i dont think they go from malgrat, but they do go from blanes.
getting a taxi all the way or from lloret or blanes may be the best option.

You can take the boat from santa susanna to tossa each day, takes about an hour nice trip, malgrat runs into santa susanna, or you can take the train from santa susanna to blanes, and then lloret, and tossa by bus, you pay for it all at the station lots cheaper than the boat and although it seems a lot of travelling it is'nt, as you get off the train the bus is waiting for you at the station, whichever way you do it it is only an hour, in fact the train and buses was about 45 mins, we did it both ways as we was in santa susana and son was in tossa, we did it three times no probs

it sounds awfully confusing and we did this trip from malgrat to tossa last year with 2 kids in tow,,,,, i thought we were going to end up in france!!
it was sooooooo easy,,,,,,,, train AND bus ticket from malgrat to lloret,, you get off the train in blanes and there are coaches out side waiting to take you to loret,,,, get on it,, then when you get off in loret there is a bus station with about 7 treminals,,, now you have to get a return ticket to tossa. the busses onyl go to certain destinations,, the tossa one goes to tossa,,,,,,,,,,, the blanes one goes to blanes they dont all go the same round route and you have to guess which stop etc,,,,,,,, there is even a blanes train station bus with a little picture of a train at the stop, so from tossa you get the bus to loret, then the bus with a train on it to blanes,,,,, then a train to malgrat about 5 minutes from there, cost, it was 5 euros each return train and bus to lloret, then a furhter 2 /3 euros each return to tossa.

Train from Malgret de Mar to Blanes and Bus takes you all the way to Tossa De Mar used it last week it costs 10 euro return